Three complementary theoretical perspectives motivate the comparison undertaken here and were used to select conditions and to interpret results.

Task-technology fit theory holds that a technology improves performance to the extent that its capabilities match the requirements of the user’s task [20]. The unified theory of acceptance and use of technology (UTAUT) and its consumer extension (UTAUT2) further specify performance expectancy, effort expectancy, and hedonic motivation as proximal determinants of use intention [21,22]. For a person living with HIV, the salient tasks are concrete: booking an anonymous test, obtaining reliable information, tracking medication. Performance expectancy and effort expectancy therefore map closely onto the MARS functionality and engagement dimensions and predict that these should dominate patient judgments. Researchers, who rate apps without a personal task to accomplish, are instead trained to apply normative criteria, so their judgments should weight information quality and safeguards more heavily.

Privacy calculus theory models disclosure as a trade-off in which anticipated benefits are weighed against perceived risk [23]. The trade-off is systematically asymmetric when risks are abstract and delayed while benefits are immediate and concrete, producing the well-documented gap between stated privacy concern and observed behavior [24]. This framework predicts that privacy protection will function as a normative criterion for expert raters but will be discounted by end users, and it makes the direction of any observed divergence theoretically interpretable rather than merely descriptive.

eHealth literacy encompasses the skills required to appraise and apply digital health information [25]. Features such as data-minimization practices and consent mechanisms are largely invisible in the interface and require appraisal skills that end users typically lack; visible features such as layout and interactivity do not. Independently of literacy, the usability literature documents an “evaluator effect”: trained evaluators applying the same instrument to the same artifact reach substantially different conclusions [26]. Together these perspectives imply that expert and user ratings should not be treated as interchangeable estimates of a single latent quality, which is the assumption implicitly embedded in current app-recommendation practice.

Each of the 3 perspectives outlined in the Theoretical Framework section describes a combination rather than an isolated effect: fit depends on functionality and content matching a task; the privacy calculus depends on risk relative to benefit. Conventional regression estimates the average, independent, symmetric contribution of each predictor [27,28] and cannot represent such conjunctions. Set-theoretic methods represent them directly through equifinality, conjunctural causation, and asymmetry [29-32].

This cross-sectional study used a comparative evaluation design to assess HIV/AIDS mobile apps. Two distinct evaluator groups were recruited: (1) professional researchers with expertise in medical informatics, computer science, and social medicine; and (2) individuals living with HIV/AIDS. The study was conducted between February and May 2023, following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines for systematic app selection [41]. The ratings analyzed here were collected for, and descriptively reported in, a previous quality evaluation of the same 21 apps [35]; the present study is a secondary, configurational analysis of that dataset, but the fuzzy-set qualitative comparative analysis (fsQCA), Wilcoxon, and sensitivity analyses reported here are new.

Two distinct matters are addressed separately here. First, the unit of analysis is the mobile app: the 21 apps are the cases on which every datum is indexed, and all calibration, necessity, sufficiency, and coverage parameters refer to sets of apps rather than to sets of people. The evaluators are not cases; within this design each evaluator functions as a measurement instrument applied to every app, which is why evaluator reliability is assessed as interrater agreement rather than treated as sampling error. Second, and separately, 5 individuals produced those measurements, 2 of them people living with HIV. The first point concerns how the ratings are analyzed; the second concerns what was owed to the individuals who produced them. The first is set out in the Evaluator Panels and Sample Size Considerations section, and the second in the Recruitment and Eligibility, Data Collected, Basis on Which Prospective Ethics Review Was Not Sought, and Protections Applied sections.

The 2 patient evaluators were recruited entirely through the HIV prevention and control team of the local Center for Disease Control and Prevention (CDC), which is the institution that maintains the follow-up records for people living with HIV in this region. The research team specified the eligibility criteria; the CDC team applied them within its own records, identified individuals who met them, and invited participation. The research team did not receive the follow-up register, did not screen or select individuals, and did not at any stage collect, request, verify or record the serostatus of either evaluator, nor their names, contact details, age, sex, place of residence or any other personal information. Serostatus was therefore never an item of information held by the research team: it was a condition applied by the CDC within data the CDC already held for its own statutory purposes. Written informed consent was obtained from both evaluators before participation; in order to protect their privacy, the consent process was conducted by the CDC team, which collected and retained the signed consent forms on behalf of the study, so that no document bearing a participant’s name passed to the research team. What the research team received were completed rating forms, identified by a study code.

The data generated in this study were MARS and uMARS scores for apps that are publicly listed in Chinese app stores and in WeChat. No biological sample, medical record, clinical measurement, health-record extract, or laboratory result was obtained from any evaluator, and no demographic, behavioral, or health variable describing an evaluator entered the dataset or any analysis. The research team therefore collected no personal information of any kind about the evaluators; the only data collected were ratings of publicly available software, held under study codes on an encrypted institutional server.

Prospective ethics review was not applied for, and the basis for that is stated here so that readers can assess it. The applicable instrument is the Measures for Ethical Review of Life Science and Medical Research Involving Humans, issued jointly by the National Health Commission, the Ministry of Education, the Ministry of Science and Technology, and the National Administration of Traditional Chinese Medicine (Guo Wei Ke Jiao Fa [2023] No. 4) [42] and in force from 18 February 2023, that is, for the whole of the evaluation period. Article 3 defines the scope of the Measures as research conducted with human beings as subjects, or conducted using human biological samples or personal information data, including health records and behavioral data; Article 50 defines a research participant correspondingly as a person who provides biological samples, information data, health records or behavioral data for the research. On both definitions, this study lies outside the scope of the Measures: no human being was a subject of investigation, no biological sample was used, and no personal information data, health record, or behavioral record of any evaluator was provided to, held by, or analyzed by the research team. What the evaluators supplied were ratings of external artifacts, which are properties of the apps rather than information about the raters. Alternatively, were the ratings to be regarded as information data supplied by identifiable individuals, Article 32(2) provides that research using anonymized information data may be exempt from ethics review where it causes no bodily harm and involves neither sensitive personal information nor commercial interest; each condition is satisfied here, since ratings were coded at source, no procedure was applied to any person, no sensitive personal information reached the research team, and the study had neither commercial sponsorship nor commercial interest. The risk to participants was no greater than the minimal-risk threshold at which Article 31 permits review by expedited procedure.

This reporting position is the prevailing one in the MARS/uMARS app-quality literature. App-quality evaluations of this design are routinely published without prospective ethics review on the ground that the object of evaluation is publicly available software rather than persons [43], and the same holds where lay end users rather than experts complete the instrument: in the Greek validation of the uMARS, in which 91 informed participants each rated an app twice, the authors reported that ethics approval was not required because the study consisted of completion of the uMARS and involved no clinical procedure [44].

Although the study lies outside the scope of mandatory review, the protections owed to participants were applied in full and in accordance with the principles of the Declaration of Helsinki. Both patient evaluators were informed of the purpose, procedures, and time commitment of the study and of their right to withdraw at any point without giving a reason and without consequence for their care, and both gave written informed consent before participating; the signed forms were collected and retained by the CDC team on their behalf. Recruitment through the CDC follow-up channel was chosen because it is the only route by which people living with HIV in this region can be approached without their status being disclosed to a third party. No information capable of identifying an evaluator appears in this article or in any associated data file.

Three researchers conducted the app evaluations using the original MARS and were purposively selected to cover the 3 competence domains that MARS scoring requires: health information content, software engineering, and app-quality methodology. Rater 1 holds a master’s degree in Medical Informatics with extensive experience in medical information analysis. Rater 2 holds a master’s degree in Computer Science with software development expertise. Rater 3 holds a PhD in Social Medicine with substantial experience in mobile app evaluation.

Before formal evaluation, all 3 raters completed MARS training by reviewing instructional videos and conducting pilot evaluations on 4 randomly selected apps (2 WeChat applets and 2 independent apps). For the formal evaluation, raters 1 and 2 independently assessed all 21 apps. To ensure consistency, evaluators completed assessment of all apps for dimension N before proceeding to dimension N+1. When discrepancies occurred between raters 1 and 2, rater 3 reassessed the app, and a consensus score was reached through structured discussion.

A total of 2 patient evaluators were recruited through collaboration with local CDC HIV prevention and control teams. Eligibility criteria, applied by the CDC team within its own follow-up records rather than by the research team, were the following: (1) confirmed HIV-positive diagnosis on the CDC follow-up register; (2) age ≥18 years; (3) ability to read and understand Simplified Chinese; and (4) experience using mobile apps. Both participants provided written informed consent, which the CDC team collected and retained on behalf of the study to protect their privacy, and both were assured of anonymity and data confidentiality; no serostatus information and no personal identifiers were transferred to the research team at any stage (see the Study Design and Ethical Considerations sections). Recruitment was purposive rather than probabilistic, with the aim of obtaining evaluators whose lived experience made them able to judge the apps as intended users.

Recruiting patient evaluators proved substantially more difficult and time-consuming than recruiting expert raters, and the size of the patient panel reflects that difficulty rather than a design preference. People living with HIV are a small and highly stigmatized minority in China, and they attach exceptional importance to the confidentiality of their serostatus. The dominant concern voiced by those who were approached and declined was not the time required by the rating protocol but the possibility that participation would create a record linking them by name to HIV-related research, however strong the assurances of anonymity. Recruitment could proceed only through the local CDC’s routine follow-up visits, which is the sole channel through which people living with HIV in this region can be approached without their status being disclosed to a third party, and a considerable period elapsed before 2 individuals willing to take part were identified. No demographic detail about the 2 participants is reported, because none was collected: in a 2-person panel recruited through a single follow-up program, age, sex and city in combination would be potentially identifying, and the research team therefore asked the CDC team not to transfer such details.

Patient evaluators completed the uMARS rather than the original MARS. They were provided with brief uMARS training materials adapted for nontechnical users, emphasizing the evaluation of user experience rather than technical specifications. Patients independently evaluated all 21 apps over a 4-week period and submitted their ratings through a secure online platform. Adequate time was provided for patients to thoroughly explore each app before rating. Patient scores were averaged across the 2 evaluators for each app and dimension.

Two aspects of sample size warrant explicit justification: the number of evaluators and the number of apps.

The use of 2 to 3 trained raters is not a constraint specific to this study but the established design convention of the MARS/uMARS app-quality literature, including in this journal. The MARS was developed and validated on independent ratings by a small expert panel and reported excellent interrater reliability under those conditions (intraclass correlation coefficient [ICC]=0.79) [15]. The convention has been maintained consistently since. Table 1 summarizes evaluator panel size across published MARS-based app-quality evaluations in JMIR mHealth and uHealth and closely related outlets, spanning instrument-validation studies, single-disease app reviews, and cross-national comparisons.

Two features of this evidence are relevant here. First, panel size does not scale with the number of apps: 2 raters were used whether 6, 7, 20, 23, 46, 50, or 104 apps were evaluated [36,47,49-53]. This is because the rater in this paradigm functions as a measurement instrument applied to each app rather than as a sampled unit of analysis. The unit of analysis is the app; the psychometric requirement is demonstrable agreement between raters, not a large rater sample. Reliability is accordingly evaluated as interrater agreement, as reported in the Interrater Agreement section, rather than treated as sampling error. Second, 3 raters—the number used for our researcher panel—is at the upper rather than the lower end of the distribution [35,54]; most comparable studies use two. Beyond the studies tabulated, the same convention is evident across app domains in this journal, including drug-drug interaction checkers [55], medication adherence apps [56], apps for deaf and hard-of-hearing users [57], hematological condition apps [58,59], traditional vs modern medicine apps in China [60], noncommunicable disease management apps [61], and apps for men who have sex with men in China [39], as well as in the Korean [46] and Arabic [62] MARS validations, in reviews of depression apps in German app stores [34] and of commercial weight-management apps [63], and in the 2 published MARS-based evaluations of HIV/AIDS apps [37,38].

The patient panel requires a separate justification, because the logic that supports a small expert panel does not transfer directly to end users: experts are trained to converge on a normative standard, whereas end users are informative partly because they differ from one another. Three considerations support the present design. First, HIV-positive status is a stigmatized and legally protected attribute in China, and recruitment is correspondingly difficult: people living with HIV could be approached only through CDC follow-up visits, and the prevailing reason for declining was concern that participation would create documentation linking the individual to HIV-related research. Second, both patient evaluators rated all 21 apps on all dimensions, so the design is complete rather than sparse: there are no missing cells, and each app is evaluated by the same evaluators, which is the condition under which paired comparison with the researcher panel is valid. Third, agreement between the 2 patient raters was examined empirically rather than assumed, and the limits of agreement were narrow relative to the rating range (see Statistical Analysis). We therefore treat the patient results as characterizing the configurational structure observed in this panel and frame them as exploratory and hypothesis-generating throughout.

Because a 2-person panel cannot stand for a population, a fixed vocabulary is used throughout. The patient panel and the 2 patient evaluators refer to the 2 individuals who completed the uMARS; patient configurations and patient-side pathways refer to configurations recovered from those 2 evaluators’ averaged ratings of the 21 apps; and statements about the researcher panel are likewise restricted to the 3 raters described in the Researcher Panel section. No expression in this paper is intended to characterize the preferences of people living with HIV in China as a population, or of Chinese app users generally. Where the text refers to patient evaluations, it refers to this panel.

Twenty-one apps are the complete set of Chinese HIV/AIDS apps meeting the inclusion criteria at the time of the search, identified from 2901 screened records. This is not a sample drawn from a larger population, but a census of an intentionally narrow population, and the small size is itself a substantive finding about the Chinese HIV/AIDS app market [35]. Comparable app-quality evaluations in this journal have analyzed as few as 4, 6, and 7 apps (Table 1), and evaluations of 20 apps have supported published quality conclusions [50].

For the configurational analysis specifically, qualitative comparative analysis (QCA) was developed for small- and intermediate-N designs and is conventionally applied to 10-50 cases, where intimate case knowledge is available, and each case can be interpreted individually [64,65]. With N=21, the present study lies within this range and, unlike most regression-based designs, permits every case to be inspected individually against its configuration. Six conditions with 21 cases nevertheless produce substantially limited diversity: of the 64 logically possible configurations, only 14 (researcher data) and 15 (patient data) contained at least one case with membership above 0.5. We therefore report the intermediate solution, which uses only easy counterfactuals [66,67]; interpret configurations alongside the specific apps that instantiate them; and report the sensitivity analyses described in the Robustness and Sensitivity Analyses section.

Six conditions were examined: engagement, functionality, aesthetics, and information quality (continuous, from MARS/uMARS); privacy protection (binary); and developer type (binary: 1=government organization, 0=nongovernment). The outcome was the subjective quality rating. Conditions were selected from the MARS/uMARS framework and from prior literature on determinants of mHealth app quality [11,15,33].

Calibration transforms raw scores into fuzzy-set membership between 0 and 1 [66,72]. Continuous conditions were calibrated using the direct method with 3 anchors set at the 95th percentile (full membership), the 50th percentile (crossover), and the 5th percentile (full nonmembership). Percentile-based anchoring is standard where no external substantive benchmark exists for the measure, and is recommended when scores are instrument-specific and their absolute values are not interpretable against a criterion [73,74]. This applies here: a MARS engagement score of 3.0 has no external meaning as a threshold of “high engagement,” whereas its position within the observed distribution of HIV/AIDS apps does. Anchors were derived separately for the researcher and patient datasets, since the 2 instruments produce different rating distributions and a common anchor would confound instrument scaling with evaluator judgment. Membership scores falling exactly at 0.50 after calibration were adjusted upward by 0.001, so that no case was left at the point of maximum ambiguity; this mattered most for patient functionality, since 14 of the 21 apps received the same functionality rating and that rating is the crossover value. Where a percentile anchor coincided with the crossover, which occurred only for patient functionality under the wider anchor sets used in the sensitivity analysis, the affected anchor was set to the nearest observed value beyond the crossover. Binary conditions were retained as crisp sets. Because the choice of percentile anchors is a researcher decision rather than a property of the data, its consequences were examined explicitly in the sensitivity analysis.

A condition is necessary if the outcome cannot occur without it [66,75]. Necessity was assessed by consistency, with the conventional threshold of 0.90 [67], and evaluated jointly with coverage to guard against trivial necessity. Both the presence and the absence of each condition were tested.

Truth tables were constructed for both datasets. A frequency cutoff of 1 was applied, as is standard for small-N designs [64], together with a raw consistency cutoff of 0.80 and a proportional reduction in inconsistency (PRI) consistency cutoff of 0.70. Boolean minimization produced complex, parsimonious, and intermediate solutions; the intermediate solution is reported as the primary result [67]. Following Fiss [76], conditions appearing in both the parsimonious and the intermediate solution are designated core, and those appearing only in the intermediate solution are designated peripheral.

Four sets of checks were performed, following current QCA reporting recommendations [64,74,77]. First, all analyses were repeated under 4 calibration anchor sets (95/50/5, 90/50/10, 85/50/15, and 80/50/20 percentiles). Second, the truth table analysis was repeated across raw consistency cutoffs of 0.75, 0.80, 0.85, and 0.90 crossed with PRI cutoffs of 0.65, 0.70, 0.75, and 0.80. Third, the analysis was repeated with the 3-level privacy set described in the Privacy Protection Assessment section. Fourth, necessity consistencies were recomputed under each anchor set. The results are considered robust where the set of configurations and their substantive interpretation are unchanged, and consistency remains above the 0.80 threshold; any specification under which this does not hold is reported explicitly.

Descriptive and comparison statistics were computed in Python 3.12; calibration, necessity analysis, and truth-table analysis were conducted in fsQCA (version 4.1; University of California). Descriptive statistics were computed for all variables. Because the 2 evaluator groups rated the same 21 apps, differences in raw dimension scores were tested with Wilcoxon signed-rank tests, with the matched rank-biserial correlation as the effect size; the nonparametric test was chosen because dimension scores were bounded, skewed, and drawn from a small sample. Agreement between groups was quantified with Pearson and Spearman correlations. Given 5 prespecified comparisons, P values should be interpreted descriptively rather than as confirmatory tests.

Agreement was examined within each panel separately, and because the 2 panels completed different instruments, no estimate reported in this section combines researcher and patient ratings. Within the researcher panel the 2 independent raters were raters 1 and 2, each of whom scored all 21 apps on the original MARS before any discrepancy was referred to rater 3 and before consensus scores were formed; Bland-Altman analysis of that MARS dataset [35,78] gave a mean difference of 0.01 (SD 0.10; 95% limits of agreement −0.19 to 0.21) for app quality and 0.07 (SD 0.49; 95% limits of agreement −0.89 to 1.03) for subjective quality. Within the patient panel, the 2 independent raters were the 2 patient evaluators whose ratings are analyzed in the present paper, each of whom scored all 21 apps on the uMARS before the 2 sets of scores were averaged; Bland-Altman analysis of that uMARS dataset gave a mean difference of 0.13 (SD 0.26; 95% limits of agreement −0.38 to 0.64) for app quality and 0.23 (SD 0.45; 95% limits of agreement −0.66 to 1.12) for subjective quality. Both uMARS estimates therefore derive specifically from the 2 patient evaluators included here, and no researcher rating enters them; conversely, the 2 MARS estimates derive only from raters 1 and 2, and no patient rating enters them.

Limits of agreement for the 2 app-quality scores are narrow relative to the 1-5 rating range, indicating close agreement within both panels; the wider limits for the single-item subjective quality scores are consistent with the greater variability expected of subjective judgments. Bland-Altman analysis was the prespecified agreement method in the parent evaluation, and it is the appropriate choice for 2 raters because it quantifies both systematic bias and the range of disagreement on the original measurement scale rather than expressing agreement relative to between-app variance [78]. An ICC could not be computed retrospectively for either panel, because the archived dataset retains only the postconsensus researcher scores and the averaged patient scores; the rater-level score files are no longer available, and the Bland-Altman estimates reported in this section are those computed in the parent evaluation while those files were still held [35]. Future apps of this design should archive rater-level scores so that both agreement statistics can be reported.

Recomputing every configuration under 4 anchor sets left the configurational structure unchanged (Table 9). Across all anchor sets, every configuration retained consistency at or above 0.942, and solution-level values remained high (researchers: consistency 0.966-0.983, coverage 0.639-0.679; patients: consistency 0.997-1.000, coverage 0.582-0.796). The baseline column of Table 9 is the set of values reported in Tables 6 and 7. Coverage was more anchor-sensitive than consistency, and most so for the patient configurations, which is expected because relaxing the full-membership anchor rescales membership scores in the outcome.

Necessity consistencies were recomputed under each anchor set. For researchers, no condition reached 0.90 under any specification, so the conclusion that no single condition is necessary for researcher judgments is not an artifact of the anchors. For patients, functionality (0.907) and information quality (0.915) exceeded the threshold at the baseline anchors only; under the three wider sets neither reached it (functionality 0.744-0.804; information quality 0.824-0.860). Two features of the patient data account for this. First, patient functionality ratings are concentrated at 4.00, so that the 80th, 85th, and 90th percentiles coincide with the crossover, and the full-membership anchor had to be set to the nearest observed value beyond it. Second, widening the anchors compresses membership scores toward the crossover and thereby lowers necessity consistency for conditions whose upper values are closely spaced. The patient necessity result is therefore anchor-dependent, which reinforces rather than qualifies the caution stated in the Necessary Conditions section: functionality is offered as a proposition for testing and not as an established necessary condition. Privacy protection remained far below threshold in every specification for both groups (0.264-0.343). The full necessity sensitivity results are given in Table 10.

Fourteen of the 64 truth table rows were empirically instantiated in the researcher data and 15 in the patient data. Under the baseline cutoffs, 6 researcher rows and 5 patient rows met both criteria. Across the 16 combinations of raw consistency cutoffs (0.75, 0.80, 0.85, 0.90) and PRI cutoffs (0.65, 0.70, 0.75, 0.80), the retained set was invariant in the patient data. In the researcher data, it was invariant with respect to the raw consistency cutoff, but the row instantiated by the Beijing AIDS Association applet, whose PRI consistency is 0.712, dropped out at PRI cutoffs of 0.75 and above, which removes configuration R5 from the solution. R5 is the contrarian pathway, is instantiated by that single case, and has the lowest consistency and the lowest raw coverage of the configurations reported; the other 4 researcher configurations were unaffected at every combination tested. The solutions are therefore insensitive to the raw consistency cutoff, and sensitive to the PRI cutoff only in respect of R5.

Re-running the analysis with the 3-level privacy set left every configuration unchanged in substance: the truth tables retained the same rows, Boolean minimization returned the same 5 researcher and 4 patient configurations, and the parsimonious solutions were identical. Consistency shifted by at most 0.018 (patient P4: 1.000 to 0.982), and no configuration fell below 0.947. Coverage changes were likewise small, the largest being increases of 0.052 in the raw coverage of patient P1 (0.285 to 0.337) and of 0.051 in that of P2 (0.474 to 0.525). Necessity consistency for privacy protection remained low under the graded specification (researchers 0.278; patients 0.223). The limited role of privacy in the patient configurations is therefore not an artifact of dichotomization: only 5 apps offered protection of any kind, only 2 of those added an in-app privacy password, and grading the 5 does not alter how privacy combines with the other conditions.

The configurations and the illustrative cases translate into a small number of concrete design decisions. They are stated below at feature level, because that is the level at which a development team acts, and recommendations that follow directly from the observed cases are distinguished from those that are proposals consistent with the findings but not themselves tested here. Table 11 sets each against the configuration from which it derives.

Functionality entered all 4 patient configurations and 3 of the 5 researcher ones, and it is the condition retained as the candidate necessary condition for the patient panel; Chabei, the illustrative case for the patient pathway P3, placed testing appointment booking 2 taps from launch. Appointment booking, reminder setting, and result checking should not sit behind a menu tree, a splash sequence, or a sign-in screen.

Information quality entered every patient configuration except P1, and registration is the point at which an identifiable record is created. The recruitment experience reported in Methods indicates how heavily that possibility weighs on this population. Content should be readable anonymously, with account creation required only for functions that cannot operate without it.

The 2 apps illustrating R3, Wu Ai Fang Hua and Ai Yi Jian, were distinguished from otherwise similar applets by a knowledge base whose entries carried attributed sources and update dates. Each content item should therefore name its source, carry a publication or revision date and, where applicable, identify the institution that reviewed it, with an in-app record of when the content set was last updated as a whole.

Privacy protection was a core condition in 3 researcher configurations and appeared as a present condition in none of the patient ones. Whatever the mechanism, a design that requires the user to seek protection out will under-protect this population. Proposals consistent with this finding, though not tested in this study, are to enable any available protection by default rather than on request, to write notification and reminder text that never names HIV status or medication, and to present what is stored and where on a single plain-language screen at first launch rather than within a terms-of-use document.

Configuration P4 reached high ratings in the patient panel on functionality and information quality alone. For a county-level team, this makes booking reliability and content currency the first 2 line items and gamified or visually elaborate features later increments. Configuration R5 makes a related point from the other side. One app reached a favorable researcher judgment on engagement alone, with functionality, aesthetics, and information quality all low; but that route appeared only in the researcher solution, rests on a single case, and has the lowest consistency and the lowest raw coverage of any configuration reported. Engagement can carry an expert’s overall impression of an app, and on the evidence here it does not stand in for the service task on the user side.

The outcome membership for Chabei (0.97) exceeded its configuration membership (0.68), which suggests a contribution from something outside the rated dimensions, most plausibly that a WeChat applet requires no download, leaves no icon on the home screen, and creates no app-store record. Where the service can be delivered in that format, the distribution format is itself a privacy feature. This reading is an interpretation of a single case rather than a measured effect.

Because privacy protection did not appear as a present condition in any patient pathway, publishing more privacy information is unlikely on its own to alter user-side judgments. A visible privacy label issued at platform or CDC level would place the appraisal burden where the capacity to carry it lies. This is a policy proposal consistent with the observed divergence rather than a finding of the study.

Several limitations bound the claims that can be made from these data.

The patient perspective rests on 2 evaluators whose ratings were averaged. Although a 2-person panel is consistent with the evaluator conventions of this literature (Table 1), and although both evaluators completed the full protocol for all 21 apps with narrow limits of agreement, 2 end users cannot capture the heterogeneity of people living with HIV in China. It is therefore not possible to determine from these data whether the patient configurations reflect preferences shared across this population or the perspectives of these 2 individuals. The patient findings are accordingly presented as exploratory and hypothesis-generating: the claim supported by these data is that a configurational logic distinct from the expert one is observable, not that it is the logic of the patient population.

Twenty-one apps with 6 conditions produce pronounced limited diversity: only 14 of 64 logically possible configurations (researcher data) and 15 of 64 (patient data) contained empirical cases. Several configurations rest on one or two apps, and unique coverage values below 0.05 (R1, R2, R4, and P1) indicate pathways with little independent empirical weight. The sensitivity analyses show the solutions are largely stable under alternative analytic choices, with the exceptions reported in the Robustness and Sensitivity Analyses section of the Results, but stability under respecification is not the same as generalizability to other app populations.

Researcher ratings came from 3 individuals from 2 institutions; although interrater agreement was close, evaluator effects cannot be excluded [26], and a differently composed expert panel might weight dimensions differently.

No interview or think-aloud data were collected, so the mechanisms proposed for the observed divergence—appraisal capacity, privacy calculus, displaced trust—are interpretations consistent with theory rather than findings.

Even under the graded specification, privacy was assessed from user-facing artifacts. Actual data handling, third-party sharing, and permission behavior were not examined, and apps that display a policy may not comply with it [70,71].

Quality was operationalized as rated subjective quality. No downstream outcome—sustained use, adherence, testing uptake, or clinical benefit—was measured, so the configurations describe pathways to a favorable evaluation, not to health impact.

Only Simplified Chinese apps available in early 2023 were examined. The market changes quickly, WeChat applets are a China-specific format, and quality drivers may differ in other linguistic and regulatory settings.