Calculating prevalence of hepatitis B in India: using population weights to look for publication bias in conventional meta-analysis.

Publication bias can result from the propensity of researchers to document what is unusual. This can distort the inferences drawn in systematic reviews. To measure the distortion, it has been suggested that a second analysis be done; using weights proportional to the size of the population from which the samples are drawn. We re-evaluate data from a published meta-analysis on prevalence of hepatitis B in India, to see how this approach alters the results. Prevalence of hepatitis B among tribal and non-tribal populations in different States was analyzed. Weights were then assigned according to population of the State. The overall country prevalence was then calculated. Using population-weights it is estimated that the point-prevalence of hepatitis B among non-tribal populations is 3.07% [95% CI: 2.5-3.64]. Among tribal populations it is 11.85% (CI 10.76-12.93). Overall prevalence was 3.70 (CI: 3.17-4.24) (corresponding to a chronic carrier rate of 2.96%). The present analysis using population-weights has resulted in the estimated prevalence among non tribal populations increasing by 24% and that among tribal populations decreasing by 25.5% when compared to figures of the meta-analysis published earlier. The advantages and drawbacks of this procedure are discussed.