Validation of a Saliva-Based Test for the Molecular Diagnosis of SARS-CoV-2 Infection

Background. Since the beginning of the pandemic, clinicians and researchers have been searching for alternative tests to improve the screening and diagnosis of the SARS-CoV-2 infection. Currently, the gold standard for virus identification is the nasopharyngeal (NP) swab. Saliva samples, however, offer clear, practical, and logistical advantages but due to a lack of collection, transport, and storage solutions, high-throughput saliva-based laboratory tests are difficult to scale up as a screening or diagnostic tool. With this study, we aimed to validate an intralaboratory molecular detection method for SARS-CoV-2 on saliva samples collected in a new storage saline solution, comparing the results to NP swabs to determine the difference in sensitivity between the two tests. Methods. In this study, 156 patients (cases) and 1005 asymptomatic subjects (controls) were enrolled and tested simultaneously for the detection of the SARS-CoV-2 viral genome by RT-PCR on both NP swab and saliva samples. Saliva samples were collected in a preservative and inhibiting saline solution (Biofarma Srl). Internal method validation was performed to standardize the entire workflow for saliva samples. Results. The identification of SARS-CoV-2 conducted on saliva samples showed a clinical sensitivity of 95.1% and specificity of 97.8% compared to NP swabs. The positive predictive value (PPV) was 81% while the negative predictive value (NPV) was 99.5%. Test concordance was 97.6% (Cohen’s Kappa = 0.86 ; 95% CI 0.81-0.91). The LoD of the test was 5 viral copies for both samples. Conclusions. RT-PCR assays conducted on a stored saliva sample achieved similar performance to those on NP swabs, and this may provide a very effective tool for population screening and diagnosis. Collection of saliva in a stabilizing solution makes the test more convenient and widely available; furthermore, the denaturing properties of the solution reduce the infective risks belonging to sample manipulation.

VALIDATION OF A SALIVA-BASED TEST FOR THE MOLECULAR DIAGNOSIS OF SARS-CoV-2 INFECTION

Background: Since the beginning of the pandemic, clinicians and researchers have been searching for alternative tests to improve screening and diagnosis of SARS-CoV-2 infection. Currently, the gold standard for virus identification is the nasopharyngeal (NP) swab. Saliva samples, however, offer clear practical and logistical advantages but due to lack of collection, transport, and storage solutions, high-throughput saliva-based laboratory tests are difficult to scale up as a screening or diagnostic tool. With this study, we aimed to validate an intra-laboratory molecular detection method for SARS-CoV-2 on saliva samples collected in a new storage and inactivating solution, comparing the results to NP swabs to determine the difference in sensitivity between the two tests. Methods: In this study, 156 patients (cases) and 1005 asymptomatic subjects (controls) were enrolled and tested simultaneously for the detection of the SARS-CoV-2 viral genome by RT-PCR on both NP swab and saliva samples. Saliva samples were collected in a preservative and inhibiting saline solution (Biofarma Srl). Internal method validation was performed to standardize the entire workflow for saliva samples. Results: The identification of SARS-CoV-2 conducted on saliva samples showed a clinical sensitivity of 95.1% and specificity of 97.8% compared to NP swabs. The positive predictive value (PPV) was 81% while the negative predictive value (NPV) was 99.5%. Test concordance was 97.6% (Cohen's Kappa=0.86; 95% CI 0.81-0.91). The LoD of the test was 5 viral copies for both samples. Conclusions: RT-PCR assays conducted on a stored saliva sample achieved similar performance to those on NP swabs and this may provide a very effective tool for population screening and diagnosis. Collection of saliva in a stabilizing solution makes the test more convenient and widely available; furthermore, the denaturation properties of the solution reduces the infective risks belonging to sample manipulation.

"A spectral criterion for the existence of the stabilizing solution of a class of Riccati type differential equations with periodic coefficients"

"In this paper, we investigate the existence and uniqueness of a stabilizing solution to a periodic backward nonlinear differential equation. This class of nonlinear equations includes as special cases many of the continuous-time Riccati equations arising both in deterministic and stochastic linear quadratic (LQ) type control problems."

The development of method of hormonal stimulation of N.L.Gerbilsky and appearance of contemporary preparations of long-term storage

The The main discovery of the 20th century in the field of fish breeding is hormonal stimulation of final stages of maturation of fish at hatcheries. The «father» of method of pituitary injections was Leningrad ichthyologist N.L. Gerbilsky. The main achievements of N.L. Gerbilsky and his school are methods of mass extraction of fish pituitaries, their dehydration by acetone for later storage and use, testing of pituitary gonadotropic activity on different objects. The induction of ovulation in female loaches Misgurnus fossilis or spermiation reaction of Galli-Mainini in male frogs Rana ridibunda or R. temporaria were used for pituitary testing. The effective doses of dried pituitaries for sturgeons were determined in milligrams and loach units or frog units. The method of pituitary injections was used for functioning of sturgeon breeding facilities at Volga, Don, Kuban and Kura and other rivers. For guaranteed answer fish breeders used hyperdoses of dry pituitary powder because its gonadotropic activity varied in dependence on stage of maturity of fish-“donors”. The followers of N.L. Gerbilsky led by Prof. I.A. Barannikova developed the technique of production of special glycerol pituitary extract (GPE) with determined gonadotropic activity. The main role in formulation of the recipe of GPE belongs to A.A. Boyev. The use of GPE has removed the problem of hyperdosing leading to worsening quality of mature germinal cells of sturgeons. Later, A.A. Boyev on the basis of this recipe with replacement of glycerol to propylene glycol created stabilizing solution of analogue of mammal LH-RH (“surphagon”) of long-term storage with concentration of active substance from 20 to 500 micrograms/ml.