Oxford Vaccine Group, University of Oxford, Oxford, United Kingdom.
NIHR Oxford Biomedical Research Centre, Oxford, United Kingdom.
PLoS Negl Trop Dis. 2020 Jan 16;14(1):e0007805. doi: 10.1371/journal.pntd.0007805. eCollection 2020 Jan.
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.
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.
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.
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.
在伤寒监测中，如果发热患者未寻求医疗，或寻求医疗但未进行血培养，则可能会漏检病例。缺失数据可能导致疾病发病率的估计不准确。
我们使用正在尼泊尔进行的儿童伤寒结合疫苗随机临床试验的数据，来确定在我们的发热诊所就诊但未进行血培养的合格患者与进行了血培养的患者相比，其患病风险是否较低。我们评估了进行血培养的临床和人口统计学预测因素，以及培养阳性结果的预测因素。使用多重插补法对缺失的血培养数据进行了插补。
在监测的第一年，记录了 2392 例发热就诊，其中 1615 例（68%）进行了血培养。如果儿童年龄较大、发热时间较长、当前体温≥38 度、或疑似伤寒或尿路感染，则更有可能进行血培养。基于插补模型，进行血培养的儿童血培养阳性发热的可能性是缺失数据的儿童的 1.87 倍。
无论研究方案如何，临床医生对发热原因的看法可能在提供血培养的决策中起重要作用。在调整因缺失血培养而漏检的病例比例的同时，还应调整因缺失数据组中培养阳性率较低而调整粗伤寒发病率估计值。
