Re: Effect on weight gain of routinely giving albendazole to preschool children during child health days in Uganda: cluster randomised controlled trial
Rapid Response re: Increased Weight Gain in Preschool Children due to Mass Albendazole Treatment Given During “Child Health Days” in Uganda: A Cluster Randomized Controlled Trial. Harold Alderman, International Food Policy Research Institute
Shortly after my paper on deworming in Uganda was published in the BMJ, I had an exchange of correspondence with Dr. Garner regarding the standard errors reported in one table. After that exchange I shared the following letter with the BMJ and with him in April 2007.
Prof. Paul Garner has kindly pointed out that, in an article published in the BMJ, my coauthors and I inadvertently failed to adjust standard errors in one of the tables for cluster based sampling. While table 2 of that paper reports means for growth in grams of 2413 [CI=2373 - 2454] and 2259 [CI=2216 - 2301] for the treatment and control groups respectively, once the design effect is taken into consideration the confidence intervals should, in fact, be [CI=2295 - 2533] and [CI=2121 - 2396].
The conclusions of the study, however, are unaffected as they are based on the multivariate regressions reported in table 3 for which the standard errors had been corrected for cluster based sampling. For example, the confidence interval for the finding that the children who attended child health days every six months where deworming medicine was provide had a significantly greater weight gain than similar children who attended child health days at which albendazole was not provided is unaffected; the CI for the difference in weight gain remains [59g - 262 g].”
Recently the BMJ has invited me to submit a letter addressing the earlier comments as well as more recent variations of that theme. I believe that it is sufficient to indicate that the results presented in the multivariate analysis remain the basis for the conclusion of the study. Given the heterogeneity of ages in the study population and the fact that the velocity of weight gain is dependent on age, table 2 was presented for background only while the primary analysis was presented in table 3. The results in this table control for these covariates as well as the duration of time between visits or the total time a child participated in the child health days organized for his or her community. These results provide more precise estimates of treatment effects.