A Rapid Antigen Detection Test to Diagnose SARS-CoV-2 Infection Using Exhaled Breath Condensate by A Modified Inflammacheck® Device

Abstract

Background: 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. Methods: 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. Results: 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). Conclusions: 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).

Aluminium Gauze Reduces SARS-CoV-2 Viral Load in Non-Woven Masks Worn by Patients with COVID-19

“…It is not known whether aerosols that permeate through non-woven masks with 99% VFE can contain SARS-CoV-2 RNA. Several studies have demonstrated that expired breath contains SARS-CoV-2 RNA or antigen [11][12][13][14][15][16]. Ours is the first study to detect SARS-CoV-2 RNA in expired breath filtered with a non-woven mask with 99% VFE.…”

Potential Use of Exhaled Breath Condensate for Diagnosis of SARS-CoV-2 Infections: A Systematic Review and Meta-Analysis

“…Twenty-one articles were then assessed and reviewed by full-text. Eventually, 7 papers [ 4 , 13 , 14 , 16 , 17 , 18 , 31 ] were included in qualitative analysis ( Table 2 ). The study from Viklund et al [ 18 ] included a total of 2 estimates, but one of them was excluded from both qualitative and quantitative analysis as the confirmatory test was a rapid antigen test rather than a RT-qPCR based one.…”

“…Overall, the systematic review included 361 samples (219 of them SARS-CoV-2 positive as confirmed by RT-qPCR; 60.7%) from 4 estimates, each of them ranging from 17 [ 13 ] to 105 [ 14 ]. Of the retrieved samples, the retrieved estimates were based on a total of 6 different tests, 5 of them commercially available, and 1 study based on a “homemade” tester [ 31 ].…”

“…More recently, the SARS-CoV-2 pandemic has substantially renewed the interest towards the potential referral to EBC as diagnostic matrix for viral pathogens, and particularly for SARS-CoV-2 [ 4 , 13 , 14 , 15 , 16 , 17 , 18 ]. For instance, a study from late 2020 has showed evidence that SARS-CoV-2 can be detected in EBC by means of RT-qPCR [ 4 , 19 ], prompting an increasing interest towards the use of alternative methods such as lateral flow assays or ELISA technologies [ 5 , 6 ].…”

“…While previous studies have reported highly inconsistent results [ 4 , 13 , 14 , 15 , 16 , 17 , 18 , 21 , 23 , 24 ], there is a substantial lack of evidence on the referral to EBC collection on diagnosis of COVID-19. An updated synthesis of the literature may be therefore useful to healthcare professionals involved in the research of new, non-invasive options for the diagnosis of SARS-CoV-2 infections.…”