Among the subgroups of FSWs, the results were correctly interpreted in 87.4% (864/988) of cases. Among the positive, negative, and invalid self-tests, misinterpretation occurred in 2.6% (0.4% positive tests with strong test bands and 2.2% positive tests with weak test bands), 18.4%, and 27.4% of cases, respectively (P < .001). The Cohen's κ coefficient was 0.79. FSWs-interpreted HIV self-test sensitivity was 88.8% (95%CI: 86.5%–90.7%) and specificity was 86.1% (95%CI: 83.6%–88.3%), which is also the percentage of participants that correctly interpreted the positive (including tests with strong or weak test bands) and negative HIV self-test results, respectively. HIV prevalence among our study participants may be estimated at 7.6%, which translates into a FSW-interpreted HIV self-test positive predictive value (PPV) of 34.4% (95%CI: 31.3%–37.6%) and negative predictive value (NPV) of 98.9% (95%CI: 97.9%–99.4%).
Among the subgroups of non-FSWs, the results were correctly interpreted in 91.6% (1571/1716) of cases. Among the positive, negative, and invalid self-tests, misinterpretation occurred in 3.8% (0.9% positive tests with strong test bands and 2.9% positive tests with weak test bands), 12.9%, and 11.4% of cases, respectively (P < .001). The Cohen's κ coefficient was 0.79. Non-FSWs-interpreted HIV self-test sensitivity was 96.9% (95%CI: 95.9%–97.7%) and specificity was 87.3% (95%CI: 85.5%–88.9%). HIV prevalence among study Non-FSW participants may be considered similar to that of the general adult population in Bunia and Kisangani at 1.6%, which translates into a Non-FSW-interpreted HIV self-test PPV of 11.0% (95%CI: 9.5%–12.7%) and NPV of 99.9% (95%CI: 99.5%–100.0%).
Finally, there was an inverse correlation between the education level and percentage of misinterpretation of results among FSW and non-FSW: FSWs with insufficient educational level incorrectly interpreted the self-test compared to those with sufficient educational level (4.3% vs 0.4%, P = .005 for positive tests, 28.3% vs 3.3%, P < .001 for negative tests, and 41.3% vs 6.7%, P < .001 for invalid tests). Among non-FSWs, no test (positive, negative or invalid) was incorrectly interpreted by participants with sufficient educational level (Fig. 2).
In bivariate analysis, the variables “commercial sex work,” “language used for the instructions for use,” and “educational level,” were factors associated with the interpretation of HIV self-test results (Table 1). In multivariate logistic regression analysis, the variables “commercial sex work” and “language used for the instructions for use” remained no more associated with the interpretation of HIV self-test results. The variable “educational level” remained associated with the interpretation of positive, negative, and invalid test results: Incorrect interpretation was higher in participants with insufficient education level than in those with sufficient education level for positive (13.1% vs 2.6%, P < .001; adjusted OR: 4.5 [95%CI: 1.8–15.8], P = .09), negative (22.3% vs 2.6%, P < .001; adjusted OR: 5.3 [95%CI: 2.8–18.0], P = .02), and invalid test results (23.8% vs 6.4%, P < .001; adjusted OR: 3.6 [95%CI: 1.8–6.6], P = .004).
We herein report on our original and recent experience of interpretation of HIV self-test results among female adult volunteers living in Kisangani and Bunia in the DRC, using a finger-stick whole-blood HIV self-test (Exacto Test HIV, Biosynex). The participants were divided as FSWs and non-FSWs according to their statement of practicing commercial sex work. The majority of items in the group of FSWs were similarly observed in the control group of non-FSWs, except instructions for use in French more frequently used in Non FSWs than FSWs, assessing high comparability between groups. In substance, the unique characteristics of FSWs could not explain by themselves the lower HIV self-test performance measurements in our study, although FSWs may have lower levels of health knowledge and higher consumption of alcohol and other psycho-active substances. In contrast, incorrect interpretation of HIV self-test results was strongly associated with low educational levels. The lower was the educational level; the greater was the difficulty to interpret the test correctly, despite frequently used notice for instructions in vernacular language (s).
Our results confirm those reported by Ortblad and colleagues on FSWs in Uganda, in the DRC, a French-speaking African country, which has its own specific cultural, economic, and societal characteristics, possibly different to those of an English-speaking country. First, incorrect interpretation of HIV self-test results was common among FSWs living in Kisangani and Bunia, since around 1 out of 9 test results were misinterpreted by FSWs in our series. As in Ortblad's report, the FSWs-interpreted HIV self-test sensitivity and specificity measurements were below 90%, which is far lower than those measured in most of the previous HIV self-testing performance studies reported in sub-Saharan Africa (≥94% sensitivity and >98% specificity).[1,3,4,17] Application of the observed sensitivity and specificity to a hypothetical group of 1000 FSWs living in the DRC with 20% of HIV prevalence would result in 22 HIV-positive FSWs being missed, and 28 HIV-negative FSWs being misidentified with a reactive test result. Furthermore, the calculated PPV in Bunia and Kisangani was very low (34.4%), indicating risk of misdiagnosis of two-third of tests interpreted as positive. Second, misinterpretation of HIV self-test occurred with each of the three test result possibilities, at seemingly high frequency (12.6%) in FSWs. The high frequency of misinterpretation in our study population differed greatly from that reported by Prazuck and colleagues in a non-trained general population living in France in which the vast majority of participants succeeded, with only 2.9% of the participants making errors, mostly when reading an invalid test. Thus, misinterpretation of inconclusive self-test results was the highest, in around 1 out 4 FSWs, as in Ortblad's report, but such results are rare in real-world settings. Incorrect HIV self-test results interpretation of negative tests in our series occurred in around 1 out of 5 FSWs, at similar frequency as in FSWs living in Uganda. For HIV positive test results, misinterpretation was more common with tests showing weak rather than strong bands, but at the difference to Ortblad's observations, the frequency of misinterpretation of HIV positive test (with weak or strong bands) was much lower in our series. These findings indicate that incorrect interpretation may occur for HIV oral fluid-based self-test as well as for capillary-based HIV self-test, and suggest that the ability to understand and correctly follow HIV self-test kit instructions for use may differ between both HIV self-tests. Finally, the development of an HIV self-test with the less as possible ambiguity to a low literacy public needs to be explored in sub-Saharan Africa.
In conclusion, our observations point that insufficient education level, rather than commercial sex work by itself, constitutes a key factor of incorrect interpretation of HIV self-test.
The authors are grateful to the volunteers for their willingness to participate in the study. Thanks are also due to Biosynex, Strasbourg, France, for providing free the Exacto Test HIV self-tests for the study. We also thank the Programme National de Lutte contre le SIDA, Kinshasa, Democratic Republic of the Congo.
S.T.-W., S.B.-A., and L.B. conceptualized the study. S.T.-W. oversaw data collection. S.T.-W., J.D.D.L. and R.-S.M.B. conducted the analysis. S.T.-W. and L.B. wrote the first draft. All authors edited the draft.
Conceptualization: Serge Tonen-Wolyec, Salomon Batina-Agasa, Laurent Bélec.
Data curation: Serge Tonen-Wolyec.
Formal analysis: Serge Tonen-Wolyec, Jean De Dieu Longo, Laurent Bélec.
Investigation: Serge Tonen-Wolyec.
Methodology: Serge Tonen-Wolyec, Salomon Batina-Agasa, Ralph-Sydney Mboumba Bouassa, Laurent Bélec.
Supervision: Salomon Batina-Agasa, Laurent Bélec.
Validation: Serge Tonen-Wolyec, Ralph-Sydney Mboumba Bouassa.
Visualization: Laurent Bélec.
Writing – original draft: Serge Tonen-Wolyec, Ralph-Sydney Mboumba Bouassa, Laurent Bélec.
Writing – review & editing: Serge Tonen-Wolyec, Laurent Bélec.
Serge Tonen-Wolyec orcid: 0000-0002-7734-7729.
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Keywords:Copyright © 2019 The Authors. Published by Wolters Kluwer Health, Inc. All rights reserved.
Democratic Republic of the Congo; female sex workers; French-speaking country; HIV; practicability; self-test; sub-Saharan Africa; WHO recommendations