1. Under-detection of blood culture-positive enteric fever cases: The impact of missing data and methods for adjusting incidence estimates.
- Author
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Voysey, Merryn, Pant, Dikshya, Shakya, Mila, Liu, Xinxue, Colin-Jones, Rachel, Theiss-Nyland, Katherine, Smith, Nicola, Shrestha, Shrijana, Basnyat, Buddha, Pollard, Andrew J., and Pitzer, Virginia E.
- Subjects
TYPHOID fever ,URINARY tract infections ,DISEASE incidence ,BACTERIAL diseases ,BLOOD ,BLOOD collection - Abstract
Background: In surveillance for typhoid fever, under-detection of cases occurs when patients with fever do not seek medical care, or seek medical care but do not receive a blood test. Missing data may result in incorrect estimates of disease incidence. Methods: We used data from an ongoing randomised clinical trial of typhoid conjugate vaccine among children in Nepal to determine if eligible patients attending our fever clinics who did not have blood taken for culture had a lower risk of disease than those who had blood drawn. We assessed clinical and demographic predictors of having blood taken for culture, and predictors of culture-positive results. Missing blood culture data were imputed using multiple imputations. Results: During the first year of surveillance, 2392 fever presentations were recorded and 1615 (68%) of these had blood cultures. Children were more likely to have blood taken for culture if they were older, had fever for longer, a current temperature ≥38 degrees, or if typhoid or a urinary tract infection were suspected. Based on imputation models, those with blood cultures were 1.87 times more likely to have blood culture-positive fever than those with missing data. Conclusion: Clinical opinion on the cause of the fever may play a large part in the decision to offer blood culture, regardless of study protocol. Crude typhoid incidence estimates should be adjusted for the proportion of cases that go undetected due to missing blood cultures while adjusting for the lower likelihood of culture-positivity in the group with missing data. Author summary: Typhoid fever is a serious illness caused by a bacterial infection in the blood. Typhoid spreads through contaminated water sources, poor sanitation or poor hygiene, and occurs most often in low-resource environments, with children being most at risk. It is hard to determine how common typhoid infections are in low-resource setting as there are many pathogens that can cause diseases with similar characteristics, and not all patients present to health-care facilities. The culture test to detect the presence of bacteria in the blood is poorly sensitive, costly to perform, and not available in all facilities. Therefore, true disease cases often go undetected, resulting in an underestimation of the true burden of disease. We examined factors associated with blood culture collection in fever patients attending typhoid surveillance clinics in Kathmandu, Nepal. We aimed to determine whether those who did not have a blood culture were different in terms of clinical and demographic characteristics to those who did have blood taken for culture and, additionally, whether they were more or less likely to test blood culture positive for typhoid fever. We provide estimates of inflation factors that can be used to adjust the crude incidence rate to account for the under-detection of typhoid cases. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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