Validation of Snort-spit Saliva in Detecting COVID-19 Using RT-PCR and Rapid Antigen Detection Test

Abstract

Objective. To determine the diagnostic accuracy of self-collected snorted and spit saliva in detecting COVID-19 using RT-PCR (ssRT-PCR) and lateral flow antigen test (ssLFA) versus nasopharyngeal swab RT-PCR (npRT-PCR).
 Methods. One hundred ninety-seven symptomatic subjects for COVID-19 testing in a tertiary hospital underwent snort-spit saliva self-collection for RT-PCR and antigen testing and nasopharyngeal swab for RT-PCR as reference. Positivity rates, agreement, sensitivity, specificity, and likelihood ratios were estimated.
 Results. Estimated prevalence of COVID-19 using npRT-PCR was 9% (exact 95% CI of 5.5% - 14.1%). A higher positivity rate of 13% in the ssRT-PCR assay suggested possible higher viral RNA in the snort-spit samples. There was 92.9% agreement between ssRT-PCR and npRT-PCR (exact 95% CI of 88.4% to 96.1%; Cohen’s Kappa of 0.6435). If npRT-PCR will be assumed as reference standard, the estimated Sensitivity was 83.3% (exact 95% CI of 60.8% to 94.2%), Specificity 93.9% (exact 95% CI of 89.3% to 96.5%), Positive predictive value of 57.7% (exact 95% CI of 38.9% to 74.5%), Negative predictive value of 98.2% (exact 95% CI of 95% to 99.4%), positive likelihood ratio of 3.65 (95% CI of 7.37 to 24.9), negative likelihood ratio of 0.178 (95% CI of 0.063 to 0.499). There was 84.84% agreement (95% exact CI of 79.1% to 89.5%; Cohen’s Kappa of 0.2356) between ssLFAvs npRT-PCR, sensitivity of 38.9% (exact 95% CI of 20.3% to 61.4%), specificity of 89.4% (exact 95% CI of 84.1% to 93.1%), PPV of 26.9% (95% CI of 13.7% to 46.1%), NPV of 93.6% (exact 95% CI of 88.8% to 96.4%), LR+ of 3.67 (95% CI of 1.79 - 7.51), LR – of 0.68 (95% CI of 0.47 - 0.99).
 Conclusion. Our data showed that snort-spit saliva RT-PCR testing had acceptable diagnostic performance characteristics and can potentially be used as an alternative to the standard nasopharyngeal/oropharyngeal swab RT-PCR test for COVID-19 in certain situations. However, our data also showed that snort-spit saliva antigen testing using lateral flow assay did not offer acceptable performance.

Salivary SARS-CoV-2 RNA for diagnosis of COVID-19 patients: A systematic review and meta-analysis of diagnostic accuracy

“…All studies were published in 2020–2022 and were conducted in Argentina [31] , Belgium [32] , Bangladesh [33] , Brazil [14] , [34] , [35] , [36] , [37] , Canada [38] , [39] , [40] , [41] , [42] , Ethiopia [43] , France [44] , [45] , Greece [46] , India [47] , Iran [48] , Italy [49] , Japan [50] , [51] , [52] , [53] , Mexico [54] , [55] , Pakistan [56] , Philippines [57] , South Korea [58] , Thailand [59] , Turkey [60] , [61] , United Arab Emirates [62] , United Kingdom [63] , United States of America [64] , [65] , [66] , [67] , [68] , [69] , [70] , [71] , [72] , [73] . The total number of participants was 14,043, and the age varied between 18 and 106 years old.…”

“…The total number of participants was 14,043, and the age varied between 18 and 106 years old. Twenty-two studies only included patients who had symptoms of COVID-19 [14] , [31] , [33] , [34] , [37] , [43] , [47] , [48] , [50] , [51] , [53] , [54] , [55] , [57] , [59] , [60] , [61] , [65] , [68] , [70] , [71] , [73] , seventeen studies included symptomatic and asymptomatic patients [32] , [35] , [36] , [38] , [39] , [41] , [42] , [44] , [45] , [46] , [49] , [58] , [62] , [63] , [64] , [66] , [69] , one study included only asymptomatic patients [52] , and four studies did not report these data [40] , [56] , [67] , [72] . Other sources of information regarding demographics, characteristics of the population, and characteristics of the samples are available in Table 2 .…”

“… Author Country Population Symptoms Diagnosis RNA extraction kit PCR-Kit Target gene for RT-PCR test Swab type Swab type Saliva collection N Age Abdollahiet et al Iran 80 (emergency unit’s triage) 56.5 ± 16.8 [24] , [25] , [26] , [27] , [28] , [29] , [30] , [31] , [32] , [33] , [34] , [35] , [36] , [37] , [38] , [39] , [40] , [41] , [42] , [43] , [44] , [45] , [46] , [47] , [48] , [49] , [50] , [51] , [52] , [53] , [54] , [55] , [56] , [57] , [58] , [59] , [60] , [61] , [62] , [63] , [64] , [65] , [66] , [67] , …”

“… NR Oro-Nasopharyngeal Whole saliva (drooling method) Guimarãeset et al Brazil 189 39.6 ± 12.3 Symptomatic patients Viral RNA detection with PCR from NPS Bio-Gene DNA/RNA Viral Extraction, by Bioclin SARS-CoV-2 molecular kit, by Bio-Manguinhos SARS-CoV-2 envelope gene Nasopharyngeal Whole saliva (spit) Hansonet et al United States of America 353 (drive-through test center) 35 [18] , [19] , [20] , [21] , [22] , [23] , [24] , [25] , [26] , [27] , [28] , [29] , [30] , [31] , [32] , [33] , [34] , [35] , [36] , [37] , [38] , [39] , [40] , [41] , [42] , [43] , [44] , [45] , [46] , [47] , [48] , [49] , [50] , [51] , [52] , [53] , [54] , [55] , [56] , [57] , [58] , [59] , [60] , …”