Estimating the incubation period of paediatric AIDS in Rwanda
Commenges, D.; Alioum, A.; Lepage, P.; Van de Perre, P.; Msellati, P.; Dabis, F.
Aids 6(12): 1515-1520
1992
ISSN/ISBN: 0269-9370 PMID: 1492934 DOI: 10.1097/00002030-199212000-00015Document Number: 324498
The authors used nonparametric and parametric methods and data on 685 AIDS cases at the Centre Hospitalier de Kigali, collected between February 1984 and December 1990, to estimate the distribution of pediatric AIDS in Kigali, Rwanda. 98.6% of the cases probably acquired AIDS via vertical transmission. A combination of the 2 Weibul distributions (parametric method) resulted in a good fit, suggesting that the sample population consisted of a subpopulation with a short incubation period and an other with a longer incubation period. The researchers could not deduce proof of heterogeneity from the shape of the distribution, however. The probability of developing AIDS during the first year of life was 0.29, which corresponded with that of the European Collaborative Study (0.26). The risk of developing pediatric AIDS increased considerably for children less than 18 months old but fell and became constant for older children. The qualitative findings matched those of a study in New York City. Even though quantitative differences between this study and the other study existed, the researchers could not compare median survival times. Since data from registers did not include HIV-infected children who had not yet developed AIDS, the researchers were not able to estimate median and mean survival periods. A possible source of bias was that the data were from a surveillance system based on cases at just 1 hospital, which probably did not see all pediatric AIDS cases. In conclusion, truncated data determined rather well the distribution of incubation periods, but could not provide much information about the scale parameters of the model.