Performance Evaluation of the SAMBA II SARS-CoV-2 Test for Point-of-Care Detection of SARS-CoV-2.

Nucleic acid amplification for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA in respiratory samples is the standard method for diagnosis. The majority of this testing is centralized and therefore has turnaround times of several days. Point-of-care (POC) testing with rapid turnaround times would allow more effective triage in settings where patient management and infection control decisions need to be made rapidly. The inclusivity and specificity of the Simple AMplification-Based Assay (SAMBA) II SARS-CoV-2 test were determined by both in silico analyses of the primers and probes and wet testing. The SAMBA II SARS-CoV-2 test was evaluated for performance characteristics. Clinical performance was evaluated in residual combined throat/nose swabs and compared to that of the Public Health England real-time PCR assay targeting the RdRp gene. The SAMBA II SARS-CoV-2 test has an analytical sensitivity of 250 copies/ml for detecting two regions of the genome (open reading frame 1ab [ORF1ab] and nucleocapsid protein [N]). The clinical performance was evaluated in 172 residual combined nose/throat swabs provided by the Clinical Microbiology and Public Health Laboratory, Addenbrooke's Hospital, Cambridge (CMPHL), which showed an estimated positive percent agreement of 98.9% (95% confidence interval [CI], 93.83 to 99.97) and negative percent agreement of 96.4% (95% CI, 89.92 to 99.26) compared to testing by the CMPHL. The data show that the SAMBA II SARS-CoV-2 test performs equivalently to the centralized testing methods, but with a shorter turnaround time of 86 to 101 min. Point-of-care tests such as SAMBA should enable rapid patient management and effective implementation of infection control measures.

Combined Point-of-Care Nucleic Acid and Antibody Testing for SARS-CoV-2 following Emergence of D614G Spike Variant.

Rapid COVID-19 diagnosis in the hospital is essential, although this is complicated by 30%-50% of nose/throat swabs being negative by SARS-CoV-2 nucleic acid amplification testing (NAAT). Furthermore, the D614G spike mutant dominates the pandemic and it is unclear how serological tests designed to detect anti-spike antibodies perform against this variant. We assess the diagnostic accuracy of combined rapid antibody point of care (POC) and nucleic acid assays for suspected COVID-19 disease due to either wild-type or the D614G spike mutant SARS-CoV-2. The overall detection rate for COVID-19 is 79.2% (95% CI 57.8-92.9) by rapid NAAT alone. The combined point of care antibody test and rapid NAAT is not affected by D614G and results in very high sensitivity for COVID-19 diagnosis with very high specificity.

Point of Care Nucleic Acid Testing for SARS-CoV-2 in Hospitalized Patients: A Clinical Validation Trial and Implementation Study.

There is an urgent need for rapid SARS-CoV-2 testing in hospitals to limit nosocomial spread. We report an evaluation of point of care (POC) nucleic acid amplification testing (NAAT) in 149 participants with parallel combined nasal and throat swabbing for POC versus standard lab RT-PCR testing. Median time to result is 2.6 (IQR 2.3-4.8) versus 26.4 h (IQR 21.4-31.4, p < 0.001), with 32 (21.5%) positive and 117 (78.5%) negative. Cohen's κ correlation between tests is 0.96 (95% CI 0.91-1.00). When comparing nearly 1,000 tests pre- and post-implementation, the median time to definitive bed placement from admission is 23.4 (8.6-41.9) versus 17.1 h (9.0-28.8), p = 0.02. Mean length of stay on COVID-19 "holding" wards is 58.5 versus 29.9 h (p < 0.001). POC testing increases isolation room availability, avoids bed closures, allows discharge to care homes, and expedites access to hospital procedures. POC testing could mitigate the impact of COVID-19 on hospital systems.

Evaluation of an easy and affordable flow cytometer for volumetric haematopoietic stem cell counting.

BACKGROUND: Accurate estimation of haematopoietic stem cell (HSC) counts by flow cytometry may be difficult in laboratories in which sophisticated equipment and staff with specific expertise are not available. Affordable flow cytometers that can perform basic functions may help to overcome these difficulties. In this study we compared HSC and leucocyte counts determined by volumetric and bead-based protocols performed with the small, low-cost Accuri(®) C6, with those obtained with two gold-standard instruments, the four-colour FACSCalibur(®) and the eight-colour FACSCantoII(®), our reference flow cytometers. MATERIALS AND METHODS: With the three cytometers we tested, in parallel, 111 consecutive samples from cord blood, peripheral blood from patients with myelofibrosis and myeloproliferative syndromes, fresh and thawed HSC collected by apheresis and bone marrow products. The findings were compared with one-way ANOVA, Bland-Altman analysis and linear regression. RESULTS: The results of HSC and leucocyte enumeration by the three devices were strongly correlated (r(2)>0.99; p<0.0001). ANOVA performed on different subgroups of samples did not reveal significant differences between HSC count determined by the C6 bead-based and reference flow cytometers in any of the subgroups. Regarding the C6 volumetric protocol, a statistically significant difference was observed only in the cord blood subgroup. Time for instrument set-up, calibration and analysis was slightly longer with Accuri(®) C6 (40 min) than with FACSCantoII(®) (30 min). DISCUSSION: Accuri(®) C6 is a reliable instrument for HSC enumeration in fresh samples, using both volumetric and bead-based approaches, although the volumetric protocol on cord blood samples needs to be improved. The Accuri(®) C6 is easy to use, does not require profound knowledge of flow cytometry and could be employed in an urgent setting. Its performance may be improved by more efficient calibration and shorter analysis time.