The ethical clearance for this study was obtained from the Tropical Disease Research Centre Ethics Committee, located at the Tropical Disease Research Centre, Zambia, under reference number TDRC IRB # TDREC/095/07/23. Permission to conduct the research was granted by the Zambia National Research Authority with reference number NHRA021/10/08/2023. The principal investigator maintained active researcher registration (NHRAR-R-389/17/05/2023) throughout the study period (04 September 2023 – 22 September 2023).

Written informed consent was obtained from all participants after a detailed explanation of the study’s objectives, procedures, potential risks, and benefits. Participation was entirely voluntary, with assurances that individuals could withdraw at any time without penalty or negative repercussions. The study collected socio-demographic data from participants but did not involve the collection or analysis of bio-samples. This approach ensured ethical compliance while focusing on self-reported experiences with the HIVST kit.

To maintain confidentiality, all participant data were de-identified and securely stored, with exclusive access granted to the study team; no third-party access was permitted. The selection of participants was unbiased, enrolling only those who met the predefined inclusion criteria.

We conducted a cross-sectional study at four high-volume health facilities in Lusaka province (04 September 2023 – 22 September 2023) to assess the user-friendliness, awareness, and usability of the CheckNOW™ blood-based HIVST kit (Abbott Rapid Diagnostic Jena [GmbH], Germany). A cross-sectional approach was chosen because it allows for a snapshot analysis of participants’ experiences, perceptions, and usability challenges at a single point in time.

Participants were randomly allocated into assisted and unassisted groups, with the assisted group receiving guidance from a trained healthcare worker or peer educator, while the unassisted group performed the self-test independently following the instructions for use. The structured study design ensured that usability factors could be compared between the two groups to assess variations in ease of use, interpretation accuracy, and willingness to recommend the test.

The study was conducted in four healthcare facilities selected for their high HIV prevalence and testing volume:

The study population included all adults aged ≥ 18 years who sought HIV testing at these facilities and were willing to use the CheckNOW™ HIVST kit.

A total of 323 CheckNOW™ HIVST kits were systematically distributed across four study facilities, with allocation proportional to each site’s average monthly testing volume. Participant recruitment occurred through consecutive random sampling during routine HIV testing services over a 14-day implementation period (04 September 2023 – 22 September 2023).

The study implemented rigorous quality control measures to ensure standardised data collection. The research questionnaire underwent formal validation (21 August 2023 – 25 August 2023) through a two-stage process involving content review by HIV testing experts followed by cognitive testing with 30 pilot participants. This validation process confirmed the instrument’s clarity and appropriateness for the study population.

Trained data collectors administered all study procedures following a comprehensive five-day training programme (28 August 2023 – 01 September 2023). The training curriculum covered proper HIVST administration, ethical consent procedures, and standardised data collection techniques. Only staff demonstrating full competency through practical assessments were certified to participate in the study.

Following test completion, trained data collectors conducted face-to-face interviews to collect comprehensive data using a structured electronic questionnaire. This included detailed socio-demographic characteristics (age, gender, urban-rural), clinical testing histories (previous HIV tests, results, and frequency), and qualitative user feedback about their testing experience. All physical documents, including signed consent forms and original test results, were securely stored in locked filing cabinets with restricted access limited to authorised study personnel only. All testing occurred in private designated spaces to ensure confidentiality and minimise external influences.

Data were validated using Microsoft Excel (Version 2016, Microsoft, Redmond, Washington, United States) before being analysed in SPSS statistics V26.0 (IBM Corp., Armonk, New York, United States). Descriptive statistics summarised participant socio-demographic characteristics, HIV testing history, usability, and awareness outcomes. The Pearson’s Chi-square or Fisher’s exact tests was used to explore associations between two categorical variables, while Mann-Whitney U test was used to compare means between two groups of participants. Statistical analysis was performed using SPSS statistics V26.0 with the level of significance set at p < 0.05. Qualitative feedback from open-ended responses was categorised thematically, identifying trends related to ease of use, challenges, and willingness to recommend the kit.

The study enrolled 316 participants across four Lusaka province facilities, demonstrating significant demographic variations. Gender distribution showed a statistically significant female predominance (56.3%, 178/316 vs male: 42.1%, 133/316; p = 0.002), with minimal missing data (1.6%, 5/316), as shown in Table 1. Age groups differed significantly from national census distributions (p < 0.001), with 25–34-year-olds representing the largest cohort (131/316, 41.5%), followed by 18–24-year-olds (35.7%, 113/316) and ≥ 35-year-olds (22.8%, 72/316). Urban residents were over-represented (60.1%, 190/316 vs rural: 39.9%, 126/316; p < 0.001). Testing history revealed exceptionally high prior engagement (95.6%, 302/316; p < 0.001 versus the national rate of 89%), with most recent tests occurring ≤ 1 year prior (61.9%, 187/302; p < 0.001), demonstrating frequent engagement with testing services. All four facilities demonstrated high testing uptake (97.8%, 316/323). Site-specific distribution patterns are shown in Table 2.

The CheckNOW™ HIVST kit exhibited outstanding usability and acceptability in the study. As shown in Table 3, 95.0% (300/316; p < 0.001) of participants found the test easy to use, with only 4.4% (14/316) reporting difficulties. Prior awareness of HIVST varied significantly (65.0%, 206/316; p < 0.001), and among those familiar with self-testing, 58.3% (120/206) had prior testing experience. Notably, a pronounced gender disparity was observed among previous users (p < 0.001): 69.2% were female participants (83/120), 29.2% were male participants (35/120), and gender information was unavailable for 1.6% (2/120). The kit demonstrated near-universal acceptability, with 98.7% (312/316; p < 0.001) of participants willing to reuse it and 99.7% (315/316; p < 0.001) recommending it to others, underscoring its potential for widespread adoption.

Figure 1 indicates participants’ experiences with the CheckNOW™ HIVST kit. Positive feedback includes responses indicating ease of use, confidence in result interpretation, satisfaction with privacy, and willingness to use or recommend the kit. Negative feedback includes reports of difficulty in blood collection, challenges with self-pricking, uncertainty in result interpretation, or preference for assisted testing. Over three-quarters (78%, 246/316) of respondents described the test as simple, though 22% (70/316) noted challenges with blood collection. More than half (65%, 205/316) expressed high trust in the accuracy of their results, while 35% (111/316) desired clearer instructions for interpretation. The majority (82%, 259/316) valued the discretion of self-testing, with 18% (57/316) suggesting improvements in packaging for enhanced confidentiality; 89% (281/316) would endorse the kit to others, citing convenience and reliability.

The CheckNOW™ HIVST kit demonstrated excellent performance in our evaluation, with statistically significant findings, as shown in Table 4. Participants showed significantly higher rates of unassisted administration (58.9%, 186/316) compared to assisted use (23.7%, 75/316; p < 0.001), indicating successful independent implementation. The accuracy of participants’ interpretation of the test results was exceptionally high at 97.5% (308/316; p < 0.001), with only 1.6% (5/316) errors. This was assessed by comparing each participant’s recorded result against a trained healthcare worker’s independent reading of the same used test device. While 83.6% (264/316) of users comprehended instructions independently, the 16.1% (51/316) requiring assistance remained statistically significant (p < 0.001), highlighting a need for enhanced instructional materials. Test results followed expected distributions, with 90.8% negative (287/316), 7.9% positive (25/316), and no invalid results. These outcomes, combined with minimal missing data and perfect test validity, confirm the kit’s robust real-world performance while identifying key opportunities for optimising user support through refined instructional aids for the 16.1% needing assistance (p < 0.001), and targeted training for healthcare workers supporting the 23.7% assisted cases.

While this study provides valuable insights into HIVST usability, three key limitations should be considered. First, the single-site urban design may limit generalisability to rural populations where national literacy rates are 37% lower than urban populations. Second, reliance on self-reported data introduces potential social desirability bias, suggesting future research should incorporate direct observational methods for more objective assessment. Finally, the cross-sectional design cannot evaluate critical longitudinal outcomes including sustained testing frequency over time, linkage-to-care rates following self-testing, or patterns of repeat test utilisation. These limitations highlight the need for multi-site longitudinal studies that combine usability assessments with clinical outcome tracking in diverse population groups.

The CheckNOW™ HIVST kit’s strong performance, evidenced by its 95.0% usability rate and 99.7% recommendation score, supports its inclusion in the national HIV testing strategy in Zambia. To maximise impact, we recommend: gender-sensitive distribution through workplaces and male-oriented community venues, and targeted awareness campaigns addressing persistent knowledge gaps. These findings contribute to growing evidence that well-designed blood-based HIVST can play a crucial role in achieving universal testing targets, particularly among populations that face barriers to facility-based testing.