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Systematic review or ‘synthesis’ of home-based voluntary HIV testing in sub-Saharan Africa: what conclusions can we reach?
Posted by tadoherty on 18 Dec 2012 at 10:16 GMT
Systematic review or ‘synthesis’ of home-based voluntary HIV testing in sub-Saharan Africa: what conclusions can we reach?
Tanya Doherty1, Karen Daniels1, Nandi Siegfried2
1Health Systems Research Unit, Medical Research Council, Cape Town, South Africa
2Department of Psychiatry and Mental Health, University of Cape Town, South Africa, and Department of Epidemiology and Biostatistics, University of California, San Francisco, USA
HIV counselling and testing (HCT) is the first step in accessing critical HIV prevention and treatment interventions. Expansion of HIV testing coverage requires innovative approaches such as home-based HIV counselling and testing (HBHCT) [1,2]. Community-based approaches to HCT have been implemented in a number of countries in sub-Saharan Africa, but little rigorous evidence of the effectiveness of this approach exists.
A Cochrane systematic review undertaken in 2007  included one cluster-randomized trial from Zambia and one pre/post-intervention (cohort) study from Uganda. The Cochrane review was updated in 2010  and only one study met the inclusion criteria, the same trial undertaken in Zambia in 2004. The review concludes that although HBHCT has the potential to enhance HCT uptake in developing countries, insufficient data exist to recommend large-scale implementation. The authors recommend that further rigorous studies are needed to determine if home-based HCT is better than facility-based HCT in improving HCT uptake.
Sabapathy and colleagues  undertook a systematic review and meta-analysis of studies reporting on uptake of HBHCT in sub-Saharan Africa. The authors should be commended for their thorough search and breadth of included papers. We would like to raise some statistical, methodological and clinical issues with respect to this meta-analysis which warrant consideration.
The review included a wide range of study designs. In addition to the single randomised controlled trial identified, studies included a retrospective cohort study, several population-based sero-prevalence surveys and descriptive reports of HBHCT interventions The review also included findings described only in a 500 word letter of correspondence  as part of the meta-analysis. It would have been useful for the authors to report the study designs in the text or tables so readers could better assess the appropriateness of pooling the data in a meta-analysis. Instead of combining the data from all the studies together we would recommend sub-grouping the meta-analysis by study design.
From a methodological standpoint assessment of study quality is increasingly recognised as an essential component of systematic review methodology of observational studies guiding decisions to meta-analyse (or not), and sensitivity analyses . In their review, Sabapathy and colleagues include an assessment of study rigour in Table 2, but only two columns relate to the rigour of the research while nine relate to the rigour of the HIV testing process. An assessment of possible sources of bias in the included studies needs greater attention given that eight of the 19 articles do not describe the sampling strategy. There is thus a high risk of selection bias which may compromise the internal validity of these studies and so too the results of the meta-analysis.
With regard to the clinical and programmatic relevance of this analysis; seven of the studies were undertaken for the primary purpose of surveying population-level HIV prevalence. There are several aspects of a household survey that are likely to be very different from a community-based HIV testing intervention: 1) individuals may feel less able to refuse consent for a questionnaire and associated blood-drawing when asked by research staff as opposed to locally appointed lay counsellors from the community they serve; 2) the method used for testing may be venous blood sampling as opposed to a rapid diagnostic test and as a consequence 3) results may not be available at the point of testing; and 4) there is likely to be less focus on pre- and post-test counselling due to the need to complete surveys on large numbers of individuals. These differences may compromise the external validity of the review for providing evidence of effectiveness to inform scale-up of this testing approach. In this regard review authors also need to take care when reporting context, ensuring that the country in which the study was conducted is correctly reported (the Kranzer et al study which was undertaken in Malawi is included under South Africa in Figure 2, Figure 3 and in the text relating to trends in testing uptake in South Africa on page 11).
Sabapathy and colleagues have provided the research community with a very helpful overview of the current state of research in HBHCT. We would argue that their review is not, and should not be viewed as, a systematic review of the effectiveness of HBHCT. The authors caution readers to interpret the results from the pooled estimates derived from heterogenous studies with care. We would go further and state that pooling results in the face of clinical, methodological and statistical heterogeneity is potentially misleading.
1. Matovu J, Makumbi F (2007) Expanding access to HIV voluntary counseling and testing in sub-Saharan Africa: alternative approaches for improving uptake, 2001-2007. Tropical Medicine & International Health 12: 1315-1322.
2. Hayes R, Sabapathy K, Fidler S (2011) Universal Testing and Treatment as an HIV Prevention Strategy: Research Questions and Methods. Curr HIV Res 9: 429-445.
3. Bateganya MH, Abdulwadud OA, Kiene SM (2007) Home-based HIV voluntary counseling and testing in developing countries. Cochrane Database Syst Rev: CD006493.
4. Bateganya M, Abdulwadud OA, Kiene SM (2010) Home-based HIV voluntary counselling and testing (VCT) for improving uptake of HIV testing. Cochrane Database Syst Rev: CD006493.
5. Sabapathy K, Van den Bergh R, Fidler S, Hayes R, Ford N (2012) Uptake of Home-Based Voluntary HIV Testing in Sub-Saharan Africa: A Systematic Review and Meta-Analysis. PLoS Med 9: e1001351.
6. Were W, Mermin J, Bunnell R, Ekwaru JP, Kaharuza F (2003) Home-based model for HIV voluntary counselling and testing. Lancet 361: 1569.
7. Siegfried N, Muller M, Deeks J, Volmink J, Egger M, et al. (2005) HIV and male circumcision--a systematic review with assessment of the quality of studies. Lancet Infect Dis 5: 165-173.
RE: Systematic review or ‘synthesis’ of home-based voluntary HIV testing in sub-Saharan Africa: what conclusions can we reach?
kalpanasabapathy replied to tadoherty on 24 Dec 2012 at 12:09 GMT
Sabapathy et al response to Doherty et. al
We thank Doherty et al. for their interest in our paper especially because their comment focuses the need for a review such as ours. They highlight the fact that the only other up-to-date attempt at assimilation of data on voluntary Home-based testing (HBT) for HIV was a Cochrane review which was unable to collate data across studies, because the inclusion and exclusion criteria only permitted the review of one paper1. In contrast, our review permitted the inclusion of observational studies and it therefore examined 524,867 recipients of an offer of HBT2.
A key finding of our review is that HBT is able to reach wide sections of communities in a diverse range of contexts and settings. We have stated that “the non-uniformity of the studies, which were nonetheless looking at uptake of a ‘uniform’ activity (the offer of an HIV test at home), could be considered both a strength and limitation of our review. While it may be a limitation for pooling results, it could also be considered a strength that even in a range of study contexts, HBT consistently achieved higher uptake than is seen in facility based testing.”
To address concerns about heterogeneity we have presented not only the contexts within which HBT was offered (see Table 1) but also the proportions of uptake for each individual study for the reader to interpret in detail in Figures 2 and 3. Similarly, we performed sub-group analyses and presented estimates for each sub-group in Figure 4 so the reader can examine the differences in the magnitude of the estimates for themselves. As such, we think it will be clear enough for readers to make their own conclusions about how large the differences were. While the primary objectives and study designs of the included studies varied, the objective of interest for our review was the uptake of HBT when offered, and they were all cross-sectional surveys for the purposes of estimating HIV test uptake.
Doherty et al argue that household prevalence surveys are likely to be different from studies offering HIV testing for the purpose of informing individuals about their HIV status. We bring their attention to Figure 4 and the sub-group analysis examining Immediate provision of result (yes/no) which effectively explores this question. There was no statistically significant difference found for this. Nor was there a difference when we examined sub-groups looking at venous blood draw vs finger-prick testing (data not shown) .
There is an important balance to be achieved between the potential for bias and loss of information when imposing criteria for study selection. Too often, systematic reviewers will equate lack of trials with lack of evidence3, but this does a disservice to policymakers who need to make decisions even in the absence of trials. Observational studies can provide strong evidence to inform policy and in certain circumstances may be the only form of evidence available where ethical or practical factors prevent preclude interventional studies. Randomized trials are not without fault4, and observational studies can yield high quality evidence5. There is no agreed system for assessing bias in observational studies6 and we displayed details relating to study process quality indicators as well as research method indicators for transparency on data which was obtainable from the papers. Randomized trials are the most reliable way to establish causal effects, but the extent to which a complex intervention like home-based testing will be taken up in a particular setting is determined by a multitude of factors that may be better evaluated through observational and operational research.
As is the case with all systematic reviews, the results of our review of HBT need to be carefully considered with respect to differences in study design, setting, and implementation. To this end, we believe it is important to provide a broad assessment of the totality of evidence, rather than limiting the evidence base to single study designs. We continue to feel that the consolidation of data in a systematic review such as ours will be of great use to policy makers.
A previous error in Figures 2 and 3 where the study by Kranzer et al was shown in a list of studies from South Africa has been rectified to indicate that this study was done in Malawi (as was always shown in Table 1). This has no effect on any of the estimates presented in the study and it does not alter any conclusions drawn in the paper.
1. Bateganya M, Abdulwadud OA, Kiene SM. Home-based HIV voluntary counselling and testing (VCT) for improving uptake of HIV testing. Cochrane database of systematic reviews 2010; (7): CD006493.
2. Sabapathy K, Van den Bergh R, Fidler S, Hayes R, Ford N. Uptake of Home-Based Voluntary HIV Testing in Sub-Saharan Africa: A Systematic Review and Meta-Analysis. PLoS Med 2012; 9(12): e1001351.
3. McCarthy G, Myers B, Siegfried N. Treatment for methaqualone dependence in adults. Cochrane database of systematic reviews 2005; (2): CD004146.
4. Rawlins M. De Testimonio: on the evidence for decisions about the use of therapeutic interventions. Clinical medicine 2008; 8(6): 579-88.
5. Guyatt GH, Oxman AD, Sultan S, et al. GRADE guidelines: 9. Rating up the quality of evidence. Journal of clinical epidemiology 2011; 64(12): 1311-6.
6. Sanderson S, Tatt ID, Higgins JP. Tools for assessing quality and susceptibility to bias in observational studies in epidemiology: a systematic review and annotated bibliography. International journal of epidemiology 2007; 36(3): 666-76.