Canine Olfactory Detection of SARS-CoV-2-Infected Humans - a Systematic Review.

Coronavirus disease 2019 (COVID-19) developed into a pandemic within months. SARS-CoV-2 testing measures and vaccines became quickly accessible. However, due to pre- or asymptomatic transmission, effective disease control remains challenging. To complement conventional testing methods, scientists around the world have investigated dogs' olfactory capability for true real-time detection. Several diseases are known to produce specific scents in affected individuals, excreted as volatile organic compounds, which can be easily detected by dogs within seconds. This systematic review evaluates the current evidence for using dogs' olfactory system as a reliable COVID-19-screening tool. Two independent procedures for study quality assessment were used: the QUADAS-2 tool for the evaluation of laboratory tests' diagnostic accuracy, designed for systematic reviews, and a second system for the general evaluation of canine scent detection studies, adapted with a focus on medical scent detection. Twenty-seven studies from thirteen countries were evaluated. Particular attention was paid to potential confounding factors, e.g., study design, patient/sample selection, dog characteristics, training protocols, and sample types/treatment. These analysis systems revealed that respectively four and six studies had low risk of bias and high quality. The four QUADAS-2 non-biased studies resulted in sensitivity and specificity ranges of 81-97% and 91-100%, whereas the six high quality studies according to the general evaluation system revealed sensitivity and specificity ranges of 82-97% and 83-100%, respectively. The other studies contained high risk of bias, concerns about the methodological applicability and/or quality concerns. Standardization and certification procedures as used for canine explosives detection should be established for medical scent detection dogs in order to use their undoubtful potential in an optimal and structured way. '.

At what times during infection is SARS-CoV-2 detectable and no longer detectable using RT-PCR-based tests? A systematic review of individual participant data.

BACKGROUND: Tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral ribonucleic acid (RNA) using reverse transcription polymerase chain reaction (RT-PCR) are pivotal to detecting current coronavirus disease (COVID-19) and duration of detectable virus indicating potential for infectivity. METHODS: We conducted an individual participant data (IPD) systematic review of longitudinal studies of RT-PCR test results in symptomatic SARS-CoV-2. We searched PubMed, LitCOVID, medRxiv, and COVID-19 Living Evidence databases. We assessed risk of bias using a QUADAS-2 adaptation. Outcomes were the percentage of positive test results by time and the duration of detectable virus, by anatomical sampling sites. RESULTS: Of 5078 studies screened, we included 32 studies with 1023 SARS-CoV-2 infected participants and 1619 test results, from - 6 to 66 days post-symptom onset and hospitalisation. The highest percentage virus detection was from nasopharyngeal sampling between 0 and 4 days post-symptom onset at 89% (95% confidence interval (CI) 83 to 93) dropping to 54% (95% CI 47 to 61) after 10 to 14 days. On average, duration of detectable virus was longer with lower respiratory tract (LRT) sampling than upper respiratory tract (URT). Duration of faecal and respiratory tract virus detection varied greatly within individual participants. In some participants, virus was still detectable at 46 days post-symptom onset. CONCLUSIONS: RT-PCR misses detection of people with SARS-CoV-2 infection; early sampling minimises false negative diagnoses. Beyond 10 days post-symptom onset, lower RT or faecal testing may be preferred sampling sites. The included studies are open to substantial risk of bias, so the positivity rates are probably overestimated.

The estimation of diagnostic accuracy of tests for COVID-19: A scoping review.

OBJECTIVES: To assess the methodologies used in the estimation of diagnostic accuracy of SARS-CoV-2 real-time reverse transcription polymerase chain reaction (rRT-PCR) and other nucleic acid amplification tests (NAATs) and to evaluate the quality and reliability of the studies employing those methods. METHODS: We conducted a systematic search of English-language articles published December 31, 2019-June 19, 2020. Studies of any design that performed tests on ≥10 patients and reported or inferred correlative statistics were included. Studies were evaluated using elements of the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) guidelines. RESULTS: We conducted a narrative and tabular synthesis of studies organized by their reference standard strategy or comparative agreement method, resulting in six categorizations. Critical study details were frequently unreported, including the mechanism for patient/sample selection and researcher blinding to results, which lead to concern for bias. CONCLUSIONS: Current studies estimating test performance characteristics have imperfect study design and statistical methods for the estimation of test performance characteristics of SARS-CoV-2 tests. The included studies employ heterogeneous methods and overall have an increased risk of bias. Employing standardized guidelines for study designs and statistical methods will improve the process for developing and validating rRT-PCR and NAAT for the diagnosis of COVID-19.