Spectrum and inoculum size effect of a rapid antigen detection test for group A streptococcus in children with pharyngitis.
Spectrum and inoculum size effect of a rapid antigen detection test for group A streptococcus in children with pharyngitis.
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DOI：
10.1371/journal.pone.0039085
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发表时间：
2012
期刊：
影响因子：
3.7
通讯作者：
Cohen R
中科院分区：
文献类型：
--
作者：
Cohen JF;Chalumeau M;Levy C;Bidet P;Thollot F;Wollner A;Bingen E;Cohen R
诊断测试准确性的稳定性对于临床医生是否可以信赖其结果至关重要。我们的目的是评估A组链球菌（GAS）的快速抗原检测试验（RADT）的性能是否受临床谱和/或细菌接种量的影响。在一项基于诊所的前瞻性多中心研究（2009-2010）中，从785名咽炎儿童中采集咽拭子。我们分析了临床谱的影响（即，McIsaac评分及其组成部分）和接种量（轻度或重度GAS生长）对RADT准确性（灵敏度、特异性、似然比和预测值）的影响，实验室咽喉培养作为参考试验。我们还评估了基于McIsaac分数的决策规则的准确性。GAS患病率为36%（95 CI：33%-40%）。85%的病例（81%-89%）的接种物较重。我们发现了对灵敏度、特异性、似然比和阳性预测值的显著谱效应（p<0.05），但对阴性预测值无显著谱效应，阴性预测值稳定在约92%。对于接种量高的儿童，RADT敏感性高于接种量低的儿童（95% vs. 40%，p<0.001）。接种量分层后，单变量和多变量分析显示，仅在接种量较轻的患者中，光谱对RADT敏感性的影响显著。基于McIsaac评分的决策规则具有99%（97%-100%）的灵敏度和52%（48%-57%）的特异性。RADT敏感性的变化仅发生在轻度接种的患者中。由于光谱效应不影响测试的阴性预测值，如果临床医生接受约10%的RADT结果阴性的儿童将有阳性的咽喉培养，那么想要排除GAS的临床医生可以依靠阴性的RADT结果，而不管临床特征如何。然而，这种政策在GAS感染并发症发生率非常低的人群中更容易接受。
The stability of the accuracy of a diagnostic test is critical to whether clinicians can rely on its result. We aimed to assess whether the performance of a rapid antigen detection test (RADT) for group A streptococcus (GAS) is affected by the clinical spectrum and/or bacterial inoculum size. Throat swabs were collected from 785 children with pharyngitis in an office-based, prospective, multicenter study (2009–2010). We analysed the effect of clinical spectrum (i.e., the McIsaac score and its components) and inoculum size (light or heavy GAS growth) on the accuracy (sensitivity, specificity, likelihood ratios and predictive values) of a RADT, with laboratory throat culture as the reference test. We also evaluated the accuracy of a McIsaac-score–based decision rule. GAS prevalence was 36% (95CI: 33%–40%). The inoculum was heavy for 85% of cases (81%–89%). We found a significant spectrum effect on sensitivity, specificity, likelihood ratios and positive predictive value (p<0.05) but not negative predictive value, which was stable at about 92%. RADT sensitivity was greater for children with heavy than light inoculum (95% vs. 40%, p<0.001). After stratification by inoculum size, the spectrum effect on RADT sensitivity was significant only in patients with light inoculum, on univariate and multivariate analysis. The McIsaac-score–based decision rule had 99% (97%–100%) sensitivity and 52% (48%–57%) specificity. Variations in RADT sensitivity only occur in patients with light inocula. Because the spectrum effect does not affect the negative predictive value of the test, clinicians who want to rule out GAS can rely on negative RADT results regardless of clinical features if they accept that about 10% of children with negative RADT results will have a positive throat culture. However, such a policy is more acceptable in populations with very low incidence of complications of GAS infection.
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