Goh Joanne W Y, Harrison Rhys, Hau Scott, Alexander Claire L, Tole Derek M, Avadhanam Venkata S
Bristol Eye Hospital, Bristol, United Kingdom.
External Disease Service, Moorfields Eye Hospital, London, United Kingdom.
Cornea. 2018 Apr;37(4):480-485. doi: 10.1097/ICO.0000000000001497.
Acanthamoeba keratitis (AK) is an uncommon but serious corneal infection, in which delayed diagnosis carries a poor prognosis. Conventional culture requires a long incubation period and has low sensitivity. Polymerase chain reaction (PCR) and in vivo confocal microscopy (IVCM) are available alternative diagnostic modalities that have increasing clinical utility. This study compares confocal microscopy, PCR, and corneal scrape culture in the early diagnosis of AK.
We reviewed the case notes of patients with a differential diagnosis of AK between June 2016 and February 2017 at the Bristol Eye Hospital, United Kingdom. Clinical features at presentation, and results of IVCM, PCR, and corneal scrape cultures were analyzed.
A total of 25 case records were reviewed. AK was diagnosed in 14 patients (15 eyes). Based on the definition of "definite AK," the diagnostic sensitivities of IVCM, PCR, and corneal scrape cultures were 100% [95% confidence interval (CI), 63.1%-100%], 71.4% (95% CI, 41.9%-91.6%) and 33.3% (95% CI, 9.9%-65.1%), respectively. The 3 methods showed a specificity of 100% and a positive predictive value of 100%. Using a reference standard of only positive corneal cultures, IVCM, and PCR had a sensitivity of 100% (95% CI, 29.2%-100%) and 75% (95% CI, 19.4%-99.4%), respectively.
All 3 diagnostic tests are highly specific, and a positive test result is highly predictive of disease presence. IVCM is both highly sensitive and specific when performed by an experienced operator. PCR is a useful adjunct in the diagnosis of AK because of its wider availability compared with IVCM, and it may be used in combination with IVCM for microbiologic confirmation.
棘阿米巴角膜炎（AK）是一种罕见但严重的角膜感染，延迟诊断预后较差。传统培养需要较长的孵育期且敏感性较低。聚合酶链反应（PCR）和活体共聚焦显微镜检查（IVCM）是具有越来越高临床实用性的可供选择的诊断方法。本研究比较共聚焦显微镜检查、PCR和角膜刮片培养在AK早期诊断中的应用。
我们回顾了2016年6月至2017年2月在英国布里斯托尔眼科医院鉴别诊断为AK的患者的病历。分析了就诊时的临床特征以及IVCM、PCR和角膜刮片培养的结果。
共回顾了25份病例记录。14例患者（15只眼）被诊断为AK。根据“确诊AK”的定义，IVCM、PCR和角膜刮片培养的诊断敏感性分别为100%[95%置信区间（CI），63.1%-100%]、71.4%（95%CI，41.9%-91.6%）和33.3%（95%CI，9.9%-65.1%）。这三种方法的特异性均为100%，阳性预测值均为100%。以仅角膜培养阳性作为参考标准时，IVCM和PCR的敏感性分别为100%（95%CI，29.2%-100%）和75%（95%CI，19.4%-99.4%）。
所有这三种诊断测试都具有高度特异性，阳性测试结果对疾病存在具有高度预测性。由经验丰富的操作人员进行IVCM检查时，其敏感性和特异性都很高。PCR因其比IVCM更容易获得，是AK诊断中的一种有用辅助手段，可与IVCM联合用于微生物学确诊。
