Factors Associated With Laboratory Test Negativity Following a Transition in Specimen Collection in Microbial Keratitis Cases

Negative laboratory results make targeting microbial keratitis treatment difficult. We investigated factors associated with laboratory negativity in patients with microbial keratitis in the context of a transition to a new specimen collection method. Microbial keratitis patients with associated laboratory tests were identified in the electronic health record of a tertiary care facility from August 2012 to April 2022. Patient demographics and laboratory results were obtained. Random sampling of 50% of charts was performed to assess the impact of the ocular history and pretreatment measures. The relationship between probability of negative laboratory results with demographics, ocular history, pretreatment measures, and utilization of a new specimen collection method (i.e. ESwab) was evaluated by multivariable logistic regression. Of 3395 microbial keratitis patients identified, 31% (n = 1051) had laboratory tests. Laboratory testing increased over time (slope = 2.5% per year, p < 0.001; 19.6% in 2013 to 42.2% in 2021). Laboratory negative rate increased over time (slope = 2.2% per year, p = 0.022; 48.5% in 2013 to 62.3% in 2021). Almost one-third of patients (31.2%, n = 164) were pretreated with steroids. Over two-thirds of patients were pretreated with antibiotics (69.5%, n = 367). 56.5% (n = 297) of patients were outside referrals. In multivariable regression, patients with corticosteroid pretreatment had lower odds of negative laboratory results (odds ratio [OR] = 0.49, p = 0.001). There were higher odds of negative laboratory results for every additional antibiotic prescribed to a patient prior to presentation (OR = 1.30, p = 0.006) and for specimens collected using ESwabs (OR = 1.69, p = 0.005). Age, prior eye trauma, outside referrals, and contact lens wear were not significantly associated with negative laboratory results. More microbial keratitis associated laboratory tests are being taken over time. Over 60% of tests were negative by 2022. Factors associated with negative laboratory test results included pretreatment with antibiotics and specimens collected with the new collection method.实验室检测结果阴性会给微生物性角膜炎（microbial keratitis）的靶向治疗带来极大困难。本研究在向新型标本采集方法过渡的背景下，探究了微生物性角膜炎患者实验室检测结果阴性的相关影响因素。我们从某三级医疗机构2012年8月至2022年4月的电子健康档案（electronic health record）中，筛选出确诊为微生物性角膜炎且完成相关实验室检测的患者，收集其人口统计学资料与实验室检测结果。我们对50%的病历进行随机抽样，以评估眼部病史与就诊前预处理措施的影响。通过多变量logistic回归（multivariable logistic regression）分析，探究了实验室检测结果阴性概率与患者人口统计学特征、眼部病史、预处理措施，以及新型标本采集方法（即ESwab）使用情况之间的关联。本研究共纳入3395例微生物性角膜炎患者，其中31%（n=1051）完成了实验室检测。实验室检测的开展比例随时间呈显著上升趋势（年增幅2.5%，p<0.001；2013年为19.6%，2021年升至42.2%）。实验室检测结果阴性率同样随时间升高（年增幅2.2%，p=0.022；2013年为48.5%，2021年达62.3%）。近三分之一的患者（31.2%，n=164）在就诊前接受了糖皮质激素预处理；超过三分之二的患者（69.5%，n=367）在就诊前使用了抗生素预处理。56.5%的患者（n=297）为外院转诊病例。多变量回归分析显示，接受糖皮质激素预处理的患者，其实验室检测结果阴性的比值比（odds ratio, OR）为0.49（p=0.001），即阴性结果发生概率更低。就诊前每额外开具一种抗生素，患者实验室检测结果阴性的比值比为1.30（p=0.006）；采用ESwab采集标本的患者，其阴性结果的比值比为1.69（p=0.005），即阴性结果发生概率更高。年龄、既往眼部外伤史、外院转诊情况以及隐形眼镜佩戴情况与实验室检测结果阴性无显著关联。近年来，微生物性角膜炎相关实验室检测的开展比例持续升高。至2022年，超过60%的实验室检测结果为阴性。与实验室检测结果阴性相关的因素包括就诊前抗生素预处理，以及采用新型ESwab标本采集方法获取标本。