Istituti Clinici Scientifici Maugeri IRCCS, 27100 Pavia, Italy.
Department of Respiratory Medicine, Boscotrecase Covid Hospital, 80042 Boscotrecase, Italy.
Sensors (Basel). 2021 Aug 25;21(17):5710. doi: 10.3390/s21175710.
The standard test that identifies the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is based on reverse transcriptase-polymerase chain reaction (RT-PCR) from nasopharyngeal (NP) swab specimens. We compared the accuracy of a rapid antigen detection test using exhaled breath condensate by a modified Inflammacheck device with the standard RT-PCR to diagnose SARS-CoV-2 infection.
We performed a manufacturer-independent, cross-sectional, diagnostic accuracy study involving two Italian hospitals. Sensitivity, specificity, positive (PLR) and negative likelihood ratio (NLR), positive (PPV) and negative predictive value (NPV) and diagnostic accuracy with 95% confidence intervals (95% CI) of Inflammacheck were calculated using the RT-PCR results as the standard. Further RT-PCR tests were conducted on NP specimens from test positive subjects to obtain the Ct (cycle threshold) values as indicative evidence of the viral load.
A total of 105 individuals (41 females, 39.0%; 64 males, 61.0%; mean age: 58.4 years) were included in the final analysis, with the RT-PCR being positive in 13 (12.4%) and negative in 92 (87.6%). The agreement between the two methods was 98.1%, with a Cohen's κ score of 0.91 (95% CI: 0.79-1.00). The overall sensitivity and specificity of the Inflammacheck were 92.3% (95% CI: 64.0%-99.8%) and 98.9% (95% CI: 94.1%-100%), respectively, with a PLR of 84.9 (95% CI: 12.0-600.3) and a NLR of 0.08 (95% CI: 0.01-0.51). Considering a 12.4% disease prevalence in the study cohort, the PPV was 92.3% (95% CI: 62.9%-98.8%) and the NPV was 98.9% (95% CI: 93.3%-99.8%), with an overall accuracy of 98.1% (95% CI: 93.3%-99.8%). The Fagan's nomogram substantially confirmed the clinical applicability of the test in a realistic scenario with a pre-test probability set at 4%. Ct values obtained for the positive test subjects by means of the RT-PCR were normally distributed between 26 and 38 cycles, corresponding to viral loads from light (38 cycles) to high (26 cycles). The single false negative record had a Ct value of 33, which was close to the mean of the cohort (32.5 cycles).
The modified Inflammacheck device may be a rapid, non-demanding and cost-effective method for SARS-CoV-2 detection. This device may be used for routine practice in different healthcare settings (community, hospital, rehabilitation).
用于识别严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）的标准检测基于鼻咽（NP）拭子标本的逆转录酶-聚合酶链反应（RT-PCR）。我们比较了使用改良的 Inflammacheck 设备检测呼出呼吸冷凝物的快速抗原检测试验与标准 RT-PCR 诊断 SARS-CoV-2 感染的准确性。
我们进行了一项制造商独立的、横断面的、诊断准确性研究，涉及两家意大利医院。使用 RT-PCR 结果作为标准，计算 Inflammacheck 的敏感性、特异性、阳性（PLR）和阴性似然比（NLR）、阳性（PPV）和阴性预测值（NPV）以及 95%置信区间（95%CI）的诊断准确性。进一步对检测呈阳性的受试者的 NP 标本进行 RT-PCR 检测，以获得作为病毒载量指示证据的 Ct（循环阈值）值。
共有 105 人（41 名女性，占 39.0%；64 名男性，占 61.0%；平均年龄：58.4 岁）纳入最终分析，其中 RT-PCR 阳性 13 例（占 12.4%），阴性 92 例（占 87.6%）。两种方法的一致性为 98.1%，Cohen's κ 评分为 0.91（95%CI：0.79-1.00）。Inflammacheck 的总体敏感性和特异性分别为 92.3%（95%CI：64.0%-99.8%）和 98.9%（95%CI：94.1%-100%），阳性似然比为 84.9（95%CI：12.0-600.3），阴性似然比为 0.08（95%CI：0.01-0.51）。考虑到研究队列中 12.4%的疾病患病率，阳性预测值为 92.3%（95%CI：62.9%-98.8%），阴性预测值为 98.9%（95%CI：93.3%-99.8%），总准确率为 98.1%（95%CI：93.3%-99.8%）。Fagan 的列线图在以 4%为预测试概率的现实场景中，极大地证实了该检测的临床适用性。通过 RT-PCR 对阳性检测对象进行检测时获得的 Ct 值在 26 到 38 个循环之间正态分布，对应于从轻（38 个循环）到高（26 个循环）的病毒载量。唯一的假阴性记录 Ct 值为 33，接近队列的平均值（32.5 个循环）。
改良的 Inflammacheck 设备可能是一种快速、不费力且具有成本效益的 SARS-CoV-2 检测方法。该设备可用于不同医疗保健环境（社区、医院、康复）的常规实践。
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