Abstract:

Objective　To improve the early diagnosis and treatment ability of atypical scrub typhus without scotoma in primary healthcare organizations in Yulin City, to effectively control the epidemic of scrub typhus, and to construct a diagnostic model for atypical scrub typhus applicable to the subtropical regions of Southern China and Southwest China. Methods　Patients with fever who were first diagnosed in the respiratory department of Yulin Red Cross Hospital from June 2016 to December 2022 were selected as the study objects. A total of 546 patients were included, including 335 males and 211 females, aged 14-100 years. Based on the characteristics of scrub typhus in three aspects: epidemiology, clinical manifestations, and physicochemical examination, the entropy weight method was applied to analyze the fever cases diagnosed as scrub typhus, atypical scrub typhus, and non-scrub typhus. The diagnostic model for atypical scrub typhus was determined after evaluation of the receiver operating characteristic curve (ROC), validation and optimization of the small samples. The diagnostic efficacy of the atypical scrub typhus diagnostic model and the Weil-Felix reaction OXK was evaluated in 77 suspected cases of scrub typhus using indirect immunofluorescent antibody test (IFAT) as the gold standard for diagnosing scrub typhus. χ² test was used. Results　Based on the percentage of each diagnostic element of scrub typhus, the prototype diagnostic model for scrub typhus/atypical scrub typhus was determined, and the optimal cut-off value for ROC curve analysis was 2.95 points, with the corresponding area under the curve (AUC) of 0.962 8, and the sensitivity and specificity were 90.0% and 100.0%, respectively. The sensitivity and specificity of the secondary evaluation of the prototype diagnostic model in a small sample (25 cases) were 90.0% and 86.7%, respectively. There was no statistically significant difference in diagnostic efficacy between the diagnostic model of atypical scrub typhus and the IFAT in scrub typhus (P>0.05), and the former's diagnosis of suspected scrub typhus cases had the following sensitivity, specificity, Youden index, compliance rate, and Kappa value of 96.7%, 70.6%, 0.67, 90.9%, and 0.72, while there was a statistically significant difference in diagnostic efficacy between the Weil-Felix reaction OXK and the IFAT (P<0.05), with corresponding diagnostic sensitivity, specificity, Youden index, compliance rate, and Kappa value of 5.0%, 100.0%, 0.05, 26.0%, and 0.02, respectively. Conclusion　The diagnostic model of atypical scrub typhus helps clinicians to objectively analyze non-specific clinical information, and provides an important reference for early diagnosis and treatment of scrub typhus, which is expected to be widely applied in primary medical institutions with limited diagnostic technology and equipment in Southern China and Southwest subtropical regions.

Key words:

Scrub typhus, atypical, Diagnosis, Entropy weight method, Model

摘要：

目的　提高玉林市基层医疗机构对无焦痂不典型恙虫病的早期诊治能力，有效控制恙虫病的疫情，构建适用于华南和西南亚热带区域的不典型恙虫病诊断模型。方法　选取2016年6月至2022年12月在玉林市红十字会医院呼吸科首诊的发热患者作为研究对象，共纳入546例患者，男性335例，女性211例，年龄14～100岁。基于恙虫病在流行病学、临床表现和理化检查3个方面的特点，应用熵权法将其划分为恙虫病、不典型恙虫病、非恙虫病3个组别。经受试者操作特征曲线（ROC）评价、小样本验证与优化，确定不典型恙虫病诊断模型。以间接免疫荧光抗体试验（IFAT）为诊断恙虫病的金标准，评价不典型恙虫病诊断模型和外斐反应OXK对77例恙虫病疑似病例的诊断效能。采用χ²检验。结果　依据恙虫病各诊断要素的占比情况，确定恙虫病/不典型恙虫病诊断模型雏形，ROC分析最佳分界值为2.95分，相应曲线下面积（AUC）为0.962 8，灵敏度和特异度分别为90.0%、100.0%，小样本（25例）对诊断模型雏形二次评价的灵敏度和特异度分别为90.0%（9例）、86.7%（13例）。不典型恙虫病诊断模型和IFAT在恙虫病诊断方面的效能差异无统计学意义（P>0.05），前者对恙虫病疑似病例诊断的灵敏度、特异度、约登指数、符合率、Kappa值分别为96.7%、70.6%、0.67、90.9%、0.72；而外斐反应OXK与IFAT相比，诊断效能方面差异有统计学意义（P<0.05），对应的诊断灵敏度、特异度、约登指数、符合率、Kappa值分别为5.0%、100.0%、0.05、26.0%、0.02。结论　不典型恙虫病诊断模型有助于临床医生客观地分析非特异性的临床资料，为早期诊断和治疗恙虫病提供重要的参考依据，有望在华南和西南亚热带区域诊断技术和设备有限的基层医疗机构推广应用。

关键词:

恙虫病, 不典型, 诊断, 熵权法, 模型