Prospective validation of a standardized questionnaire for estimating childhood mortality and morbidity due to pneumonia and diarrhoea

This paper reports the validation of a 'best-judgement' standardised questi onnaire using guidelines and algorithms developed by an expert working grou p conducted in Nicaragua between 1995 and 1997. Prospective hospital data, including standardised medical recording of selected signs and symptoms, la boratory and radiographic test results and physician diagnoses were collect ed for children < 5 years admitted with any serious life-threatening condit ion in 3 study hospitals. The mothers or caregivers of the children were la ter traced and interviewed using the 'best-judgement' questionnaire. Interv iews were completed 1-22 months after admission to hospital for 1115 childr en (400 who died during the stay in hospital and 715 who were discharged al ive). The cause of death or admission to hospital was determined by an expe rt algorithm applied to hospital data. A similar procedure was used to deri ve the cause using the answers to questions from interviews. Hospital cause s were compared with interview causes and sensitivity and specificity calcu lated, together with the estimated cause-specific fraction for diarrhoea an d pneumonia. Multiple diagnoses were allowed; 378 children in the sample (1 04 deaths, 274 survivors) had a reference diagnosis of diarrhoeal illness, and 506 (168 deaths, 338 survivors) a reference diagnosis of pneumonia. Whe n results for deaths and survivors in all age groups were combined, the exp ert algorithms had sensitivity between 86% and 88% and specificity between 81% and 83% for any diarrhoeal illness; and sensitivity between 74% and 87% and specificity between 37% and 72% for pneumonia. Algorithms tested in pr evious validation studies were also applied to data obtained in this study and the results are compared. Despite less than perfect sensitivity and spe cificity, reasonably accurate estimates of the cause-specific mortality and morbidity fractions for diarrhoea were obtained, although the accuracy of estimates in other settings using the same instrument will depend on the tr ue cause-specific fraction in those settings. The algorithms tested for pne umonia did not produce accurate estimates of the cause-specific fraction, a nd are not recommended for use in community settings.