Department of Infectious Disease, Tan Tock Seng Hospital, Singapore.
PLoS One. 2009 Dec 29;4(12):e8453. doi: 10.1371/journal.pone.0008453.
The presentation of new influenza A(H1N1) is broad and evolving as it continues to affect different geographic locations and populations. To improve the accuracy of predicting influenza infection in an outpatient setting, we undertook a comparative analysis of H1N1(2009), seasonal influenza, and persons with acute respiratory illness (ARI) in an outpatient setting.
METHODOLOGY/PRINCIPAL FINDINGS: Comparative analyses of one hundred non-matched cases each of PCR confirmed H1N1(2009), seasonal influenza, and ARI cases. Multivariate analysis was performed to look for predictors of influenza infection. Receiver operating characteristic curves were constructed for various combinations of clinical and laboratory case definitions. The initial clinical and laboratory features of H1N1(2009) and seasonal influenza were similar. Among ARI cases, fever, cough, headache, rhinorrhea, the absence of leukocytosis, and a normal chest radiograph positively predict for both PCR-confirmed H1N1-2009 and seasonal influenza infection. The sensitivity and specificity of current WHO and CDC influenza-like illness (ILI) criteria were modest in predicting influenza infection. However, the combination of WHO ILI criteria with the absence of leukocytosis greatly improved the accuracy of diagnosing H1N1(2009) and seasonal influenza (positive LR of 7.8 (95%CI 3.5-17.5) and 9.2 (95%CI 4.1-20.3) respectively).
CONCLUSIONS/SIGNIFICANCE: The clinical presentation of H1N1(2009) infection is largely indistinguishable from that of seasonal influenza. Among patients with acute respiratory illness, features such as a temperature greater than 38 degrees C, rhinorrhea, a normal chest radiograph, and the absence of leukocytosis or significant gastrointestinal symptoms were all positively associated with H1N1(2009) and seasonal influenza infection. An enhanced ILI criteria that combines both a symptom complex with the absence of leukocytosis on testing can improve the accuracy of predicting both seasonal and H1N1-2009 influenza infection.
新的甲型 H1N1 流感的表现广泛且不断变化，因为它继续影响不同的地理位置和人群。为了提高在门诊环境中预测流感感染的准确性，我们对门诊环境中甲型 H1N1（2009 年）、季节性流感和急性呼吸道疾病（ARI）患者进行了比较分析。
方法/主要发现：对 100 例经 PCR 确认的甲型 H1N1（2009 年）、季节性流感和 ARI 病例进行了非匹配病例的比较分析。进行了多变量分析以寻找流感感染的预测因素。为各种临床和实验室病例定义组合构建了接收者操作特征曲线。甲型 H1N1（2009 年）和季节性流感的初始临床和实验室特征相似。在 ARI 病例中，发热、咳嗽、头痛、流涕、白细胞不增多和正常胸部 X 线片均为 PCR 确诊的甲型 H1N1-2009 和季节性流感感染的阳性预测因素。目前世界卫生组织和疾病预防控制中心流感样疾病（ILI）标准预测流感感染的敏感性和特异性均较低。然而，将世界卫生组织 ILI 标准与白细胞不增多结合使用可大大提高诊断甲型 H1N1（2009 年）和季节性流感的准确性（阳性似然比分别为 7.8（95%CI 3.5-17.5）和 9.2（95%CI 4.1-20.3））。
结论/意义：甲型 H1N1（2009 年）感染的临床表现与季节性流感基本无法区分。在急性呼吸道疾病患者中，体温高于 38°C、流涕、胸部 X 线正常以及白细胞不增多或无明显胃肠道症状等特征均与甲型 H1N1（2009 年）和季节性流感感染呈正相关。一种增强的 ILI 标准，将症状综合与检测时白细胞不增多结合起来，可以提高预测季节性流感和 H1N1-2009 流感感染的准确性。
