A single weighting approach to analyze respondent-driven sampling data.

BACKGROUND AND OBJECTIVES: Respondent-driven sampling (RDS) is widely used to sample hidden populations and RDS data are analyzed using specially designed RDS analysis tool (RDSAT). RDSAT estimates parameters such as proportions. Analysis with RDSAT requires separate weight assignment for individual variables even in a single individual; hence, regression analysis is a problem. RDS-analyst is another advanced software that can perform three methods of estimates, namely, successive sampling method, RDS I and RDS II. All of these are in the process of refinement and need special skill to perform analysis. We propose a simple approach to analyze RDS data for comprehensive statistical analysis using any standard statistical software. METHODS: We proposed an approach (RDS-MOD - respondent driven sampling-modified) that determines a single normalized weight (similar to RDS II of Volz-Heckathorn) for each participant. This approach converts the RDS data into clustered data to account the pre-existing relationship between recruits and the recruiters. Further, Taylor's linearization method was proposed for calculating confidence intervals for the estimates. Generalized estimating equation approach was used for regression analysis and parameter estimates of different software were compared. RESULTS: The parameter estimates such as proportions obtained by our approach were matched with those from currently available special software for RDS data. INTERPRETATION & CONCLUSIONS: The proposed weight was comparable to different weights generated by RDSAT. The estimates were comparable to that by RDS II approach. RDS-MOD provided an efficient and easy-to-use method of estimation and regression accounting inter-individual recruits' dependence.

Relapse and deformity among 2177 leprosy patients released from treatment with MDT between 2005 and 2010 in South India: A retrospective cohort study.

OBJECTIVE: To estimate the incidence of relapse among leprosy patients released after completing multi-drug therapy (MDT) during 2005-2010 under India's National Leprosy Eradication Programme in South India. METHODS: We conducted a retrospective cohort study of leprosy patients who were released from treatment (RFT) with MDT during April 2005 and March 2010 in four purposely selected districts from South India. We clinically examined them for signs of relapse, persistence and deformity. We collected slit skin smears from those reporting signs of relapse or persistence. We computed relapse rate per 1000 person years by dividing the number of relapses by person years of follow-up and 95% confidence intervals (CI) for rates. FINDINGS: We tracked 3791 RFT patients and examined 58% of them. The examined and those who were not examined were similar in terms of leprosy type, year of completing MDT and gender. We identified 58 relapses (relapse rate 6.1 per 1000 person years) among the examined. Majority of these relapses occurred within 3 years post-MDT. Eighteen (31%) of the relapsed patients had deformity. CONCLUSION: While low level of relapse indicates effectiveness of MDT, the burden of deformity is of concern. For maximizing treatment effectiveness and minimizing transmission, we recommend educating leprosy patients at treatment completion for self-monitoring of signs of relapse and advising them to visit nearby public health facilities or Community health workers for immediate evaluation and intervention.

Measles case fatality rate in Bihar, India, 2011-12.

BACKGROUND: Updated estimates of measles case fatality rates (CFR) are critical for monitoring progress towards measles elimination goals. India accounted for 36% of total measles deaths occurred globally in 2011. We conducted a retrospective cohort study to estimate measles CFR and identify the risk factors for measles death in Bihar-one of the north Indian states historically known for its low vaccination coverage. METHODS: We systematically selected 16 of the 31 laboratory-confirmed measles outbreaks occurring in Bihar during 1 October 2011 to 30 April 2012. All households of the villages/urban localities affected by these outbreaks were visited to identify measles cases and deaths. We calculated CFR and used multivariate analysis to identify risk factors for measles death. RESULTS: The survey found 3670 measles cases and 28 deaths (CFR: 0.78, 95% confidence interval: 0.47-1.30). CFR was higher among under-five children (1.22%) and children belonging to scheduled castes/tribes (SC/ST, 1.72%). On multivariate analysis, independent risk factors associated with measles death were age <5 years, SC/ST status and non-administration of vitamin A during illness. Outbreaks with longer interval between the occurrence of first case and notification of the outbreak also had a higher rate of deaths. CONCLUSIONS: Measles CFR in Bihar was low. To further reduce case fatality, health authorities need to ensure that SC/ST are targeted by the immunization programme and that outbreak investigations target for vitamin A treatment of cases in high risk groups such as SC/ST and young children and ensure regular visits by health-workers in affected villages to administer vitamin A to new cases.