Background: Diarrhea is a leading cause of death among children under five globally. Most studies of pediatric diarrhea rely on caregiver-reported stool consistency and frequency to define disease.
Methods: We collected stool samples from 2398 children participating in two water-improvement intervention trials in the Amhara region of Ethiopia. In the smaller trial we examined the pediatric enteric virome across stool consistency to evaluate differences in species richness and community composition using metagenomic sequencing. We also measured caregiver-reported pediatric diarrhea as an outcome for this trial, and performed bias analysis to estimate the impact of misclassified diarrhea on the trial outcome. The consistency of each stool sample was graded by the child’s caregiver and two trained laboratory technicians according to an illustrated stool consistency scale. We assessed the reliability of graded stool consistency among the technicians, then compared the caregiver’s grade to the first technician’s grade. Caregivers were asked to report if children had three or more loose or watery stools in a 24-hour period anytime in the past seven days.
Results: The sensitivity of caregiver-reported loose or watery stool was 15.5 [95 CI: 9.7, 24.2] and the specificity was 98.4 [95CI 97.1, 99.1]. Species richness was highest in watery-consistency stool and decreased as stool consistency became firmer (Spearman's r=-0.45, p=0.013). The greatest differential abundance comparing loose or watery to formed stool was for norovirus GII (7.64, 95 CI 5.8, 9.5) followed by aichivirus A (5.93, 95 CI 4.0, 7.89) and adeno-associated virus 2 (5.81, 95CI 3.9, 7.7).
Conclusions: Caregiver reported stool consistency using the terms ‘loose or watery’ does not accurately describe stool consistency as graded by trained laboratory technicians. Given the predominance of using caregiver-reported stool consistency to define diarrheal disease, the low sensitivity identified in this study suggests that the burden of diarrheal disease may be underestimated and intervention effects could be biased. We documented a difference in pediatric enteric virome according to mBSFS-C stool consistency category. Bias analysis did not reveal a corrected protective effect of the water-improvement intervention.