Laryngotracheal aspiration test reduce the false negative rate in patients with suspected SARS-COV-2 pneumonia despite a negative nasopharyngeal swab

Strategies to Overcome Erroneous Outcomes in Reverse Transcription-Polymerase Chain Reaction (RT-PCR) Testing: Insights From the COVID-19 Pandemic

The reverse transcription-polymerase chain reaction (RT-PCR) test to detect SARS-CoV-2, the virus causing COVID-19, has been regarded as the diagnostic gold standard. However, the excessive sensitivity of RT-PCR may cause false-positive outcomes from contamination. Again, its technical complexity increases the chances of false-negatives due to pre-analytical and analytical errors. This narrative review explores the elements contributing to inaccurate results during the COVID-19 pandemic and offers strategies to minimize these errors. False-positive results may occur due to specimen contamination, non-specific primer binding, residual viral RNA, and false-negatives, which may arise from improper sampling, timing, labeling, storage, low viral loads, mutations, and faulty test kits. Proposed mitigation strategies to enhance the accuracy of RT-PCR testing include comprehensive staff training in specimen collection, optimizing the timing of tests, analyzing multiple gene targets, incorporating clinical findings, workflow automation, and implementing stringent contamination control measures. Identifying and rectifying sources of error in RT-PCR diagnosis through quality control and standardized protocols is imperative for ensuring quality patient care and effective epidemic control.

Sampling from upper and/or lower respiratory tract when diagnosing coronavirus disease 2019 (COVID-19) - results from a Danish cohort study

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can replicate in the upper and lower respiratory tract. We aimed to evaluate whether symptom characteristics and symptom duration prior to sampling are associated with test positivity in upper or lower respiratory tract samples.

METHODS

We conducted a retrospective cohort study in the Central Denmark Region from 14 April 2020 to 2 November 2020 including hospitalised patients with SARS-CoV-2 reverse transcriptase-polymerase chain reaction samples from both the upper and lower respiratory tract within 48 h and at least one positive test result.

RESULTS

Of 122 patients, 101 were positive in both samples (83%), 7 (5%) were positive only in the upper respiratory tract sample, and 14 (11%) were only positive in the lower respiratory tract sample. The median number of symptoms was 4 (IQR 3, 5.75) and 5 (IQR 3, 7), respectively, in patients with only a positive upper respiratory tract sample and in concordant positive patients; while 1 (IQR 1, 3) in patients with only a positive upper respiratory tract sample. 98% (120/122) of patients would have been diagnosed with coronavirus disease 2019 if supplemental sampling from the lower respiratory tract was guided by lower respiratory tract symptoms. No substantial difference in the duration of symptoms was observed across the three patient groups.

CONCLUSIONS

The presence of lower respiratory tract symptoms could have been used to determine whether supplemental sampling from the lower respiratory tract was necessary. Symptom duration was not associated with test positivity in the upper or lower respiratory tract.

Evaluation of SARS-CoV-2 antibody persistence and viral spread in stool: a long-term care experience before COVID-19 vaccination

BACKGROUND

Due to elderly residents, nursing homes/assisted living facilities were the most affected places in COVID-19 pandemic. Besides symptomatic patients, asymptomatic patients were detected during routine screening.

AIM

This study aims to determine the factors that affect antibody response and viral shedding in stool samples after natural exposure to the virus in residents and staff who recovered from COVID-19 before the vaccine was available.

METHODS

This prospective cross-sectional study was conducted at the nation's highest-capacity Residential and Nursing Home. Blood samples were collected between December 15, 2020 and January 15, 2021 from participating residents and staff for anti-SARS-CoV-2 antibody testing. Stool samples were obtained for SARS-CoV-2 PCR testing 2 months after COVID-19. The Social Sciences (SPSS) program version 15.0 was used for statistical analysis. The Mann-Whitney U test compared SARS-CoV-2 antibody concentration between two groups.

RESULTS

Four hundred sixty-four (52.3%) residents and 424 (47.7%) staff participated. Entirely 259 (29.2%) participants were anti-SARS-CoV-2 IgG (+) and 255 (28.7%) were SARS-CoV-2 PCR (+). Both antibody and PCR positivity was detected in 196 (76.9%). In PCR (-) group, 63 (10.0%) participants were SARS-CoV-2 IgG (+). Antibody titers were found highest in SARS-CoV-2 PCR (+) male residents. SARS-CoV-2 IgG titers were significantly high in SARS-CoV-2 PCR (+) and hospitalized participants regardless of age. Stool samples were obtained from 61(23.9%) participants and were found negative.

CONCLUSION

A durable SARS-CoV-2 IgG antibody response was monitored at least 9 months after the participants were diagnosed with COVID-19. SARS-CoV-2 antibody positivity was detected 76.9% in PCR (+) and 10.0% in PCR (-) participants. Knowing the duration of detectable antibodies is an important finding for developing disease prevention and public health strategies.

A Comparison of Pharyngeal Swabs and Tracheal Secretions for the Diagnosing of COVID-19

The aim of this study was to compare the test results from patients who, within a short timescale, have been tested for COVID-19 using both a pharyngeal swab and tracheal secretion. Data were collected from the database of AUH, from patients hospitalized between 1 March 2020 and 1 March 2021 who, due to symptoms of COVID-19, were tested by a pharyngeal swab and by tracheal secretion. We found great agreement between oropharyngeal swab and tracheal secretion RT-PCR testing for the diagnosis of COVID-19, with 98.5% of double tests being concordant and only 1.5% being discordant. This finding may advocate a single-test strategy being either an oropharyngeal swab RT-PCR testing or tracheal secretion, although this study revealed 15.9% false negative oropharyngeal swabs.

Comparison of nasopharyngeal swab and nasopharyngeal aspiration in adults for SARS-CoV-2 identification using reverse transcription-polymerase chain reaction

We aimed to compare reverse transcription‐polymerase chain reaction (RT‐PCR) results of nasopharyngeal aspiration (NA) and nasopharyngeal swab (NS) samples in the diagnosis of coronavirus disease 2019. NS was obtained with a dacron swab and NA was performed by aspiration cannula. The sampling was performed by an otolaryngologist to ensure standardized correct sampling from the nasopharynx. RT‐PCR was performed for the detection of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2). The level of agreement between the result of NA and NS samples for each patient was analyzed. The Ct values were compared. Thirty‐three patients were enrolled in the study with a mean age of 56.3 years. Thirteen subjects resulted negative with both NS and NA; 20 subjects resulted positive with NA and 18 subjects resulted positive with NS. The mean values of Ct for NA samples and NS samples were 24.6 ± 5.9 and 24 ± 6.7, respectively. There was no statistical difference between Ct values of NA and NS samples (p = 0.48). RT‐PCR for SARS‐Cov2 performed with NA sample and NS sample showed a strong correlation regarding the positivity/negativity and the Ct values.

The results demonstrated that RT–PCR for SARS–Cov2 performed with NA sample and NS sample showed a strong correlation regarding the positivity and negativity and the Ct values.

It is less likely to obtain an insufficient amount of material with NA than that with NS. Therefore, NA may be preferred for the second sampling, especially in patients who are difficult to be sampled with swab because of a septal deviation or patient incompatibility.

Optimal Insertion Depth for Nasal Mid-Turbinate and Nasopharyngeal Swabs

Millions of people are tested for COVID-19 daily during the pandemic, and a lack of evidence to guide optimal nasal swab testing can increase the risk of false-negative test results. This study aimed to determine the optimal insertion depth for nasal mid-turbinate and nasopharyngeal swabs. The measurements were made with a flexible endoscope during the collection of clinical specimens with a nasopharyngeal swab at a public COVID-19 test center in Copenhagen, Denmark. Participants were volunteer adults undergoing a nasopharyngeal SARS-CoV-2 rapid antigen test. All 109 participants (100%) completed the endoscopic measurements; 52 (48%) women; 103 (94%) white; mean age 34.39 (SD, 13.2) years; and mean height 176.7 (SD, 9.29) cm. The mean swab length to the posterior nasopharyngeal wall was 9.40 (SD, 0.64) cm. The mean endoscopic distance to the anterior and posterior end of the inferior turbinate was 1.95 (SD, 0.61) cm and 6.39 (SD, 0.62) cm, respectively. The mean depth to nasal mid-turbinate was calculated as 4.17 (SD, 0.48) cm. The optimal depths of insertion for nasal mid-turbinate swabs are underestimated in current guidelines compared with our findings. This study provides clinical evidence to guide the performance of anatomically correct nasal and nasopharyngeal swab specimen collection for virus testing.