Meier P A, Mathers W D, Sutphin J E, Folberg R, Hwang T, Wenzel R P
Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, USA.
Arch Ophthalmol. 1998 Aug;116(8):1090-4. doi: 10.1001/archopht.116.8.1090.
To investigate an outbreak of presumed Acanthamoeba keratitis (AK), to identify risk factors associated with its development, and to characterize the changing epidemiology of AK.
We performed a pairwise-matched case-control study involving 31 patients who were diagnosed as having AK between July 1993 and December 1994. Risk factors were identified using conditional logistic regression analysis. To investigate the impact of regional flooding, we stratified counties within Iowa by whether their water facilities were affected and then calculated population-based estimates of the incidence of AK.
During the study, 43 presumed incident cases of AK were diagnosed; 31 were included in the case-control study. Cases were diagnosed based on the clinical presentation of keratitis, positive tandem scanning confocal microscopy examination results, and confirmatory cytopathologic findings. There were no positive culture specimens. On average, cases had symptoms for 8 weeks before diagnosis, most notably photophobia (94%), red eyes (94%), and pain (80%). Contact lens use (odds ratio [OR] = 44.16; P = .02) and fishing (OR = 22.62; P = .04) were independent predictors of the development of AK. The presence of a humidifier in the home (OR = 0.08; P = .03) and having household water that originated from a private well instead of the municipal water supply (OR = 0.12; P = .08) were protective. Twenty-nine of 30 cases resided in counties in which the water supplies were affected by flooding as determined by the Department of Natural Resources, Des Moines, Iowa. The incidence of AK in these counties was more than 10 times higher than that in the unaffected counties (relative risk = 10.83, 95% confidence interval, 1.48-79.49; P < .003).
We describe an epidemic of keratitis that, based on clinicopathologic and epidemiological evidence, is consistent with AK. As in previous outbreaks of culture-proven AK, contact lens use was the major risk factor. Both the results of the case-control study and the population-based incidence estimates suggest that the recent outbreak may be caused, in part, by the effects of regional flooding. However, because the outbreak also coincided with a change in diagnostic techniques, we cannot eliminate recognition bias as the reason for the apparently changing epidemiology.
调查疑似棘阿米巴角膜炎（AK）的暴发情况，确定与其发生相关的危险因素，并描述AK不断变化的流行病学特征。
我们进行了一项配对病例对照研究，纳入了1993年7月至1994年12月期间被诊断为患有AK的31例患者。使用条件逻辑回归分析确定危险因素。为了调查区域洪水的影响，我们根据爱荷华州各县的供水设施是否受影响进行分层，然后计算基于人群的AK发病率估计值。
在研究期间，共诊断出43例疑似AK新发病例；31例纳入病例对照研究。病例根据角膜炎的临床表现、串联扫描共聚焦显微镜检查结果阳性以及确诊的细胞病理学发现进行诊断。培养标本均为阴性。病例在诊断前平均有症状8周，最常见的是畏光（94%）、眼红（94%）和疼痛（80%）。佩戴隐形眼镜（优势比[OR]=44.16；P=0.02）和钓鱼（OR=22.62；P=0.04）是AK发生的独立预测因素。家中有加湿器（OR=0.08；P=0.03）以及家庭用水来自私人水井而非市政供水（OR=0.12；P=0.08）具有保护作用。根据爱荷华州得梅因市自然资源部的判定，30例病例中有29例居住在供水受洪水影响的县。这些县的AK发病率比未受影响的县高10倍以上（相对危险度=10.83，95%置信区间，1.48 - 79.49；P<0.003）。
我们描述了一场角膜炎的流行，根据临床病理和流行病学证据，与AK一致。与之前经培养证实的AK暴发一样，佩戴隐形眼镜是主要危险因素。病例对照研究结果和基于人群的发病率估计均表明，近期的暴发可能部分是由区域洪水的影响所致。然而，由于此次暴发也恰逢诊断技术的变化，我们不能排除识别偏倚是流行病学明显变化的原因。
