Evaluation of the Elecsys SARS-CoV-2 antigen assay for the detection of SARS-CoV-2 in nasopharyngeal swabs.

AIMS: The aim of this study was to evaluate the performance of the automated Elecsys® SARS-CoV-2 antigen assay compared to RT-PCR taken as the gold standard for SARS-CoV-2 detection. METHODS: 225 nasopharyngeal swabs were randomly collected among which 123 were tested positive and 102 negatives for SARS-CoV-2 based on RT-PCR. Antigen dosing were performed on a Cobas 8000 e801 analyzer. RESULTS: The antigen test diagnosed SARS-CoV-2 infection status with an overall sensitivity of 65,85% (95% CI 56,76-74,16%), a specificity of 100% (95% CI 96,49-100%) with a Cut-off value ≥ 1. When the cut-off value for the antigen assay was set to > 0,673 COI, the accuracy reached its highest level with a sensitivity of 74,8% (95% CI 66,2 - 82,2%) and a specificity of 97,1% (95% CI 91,6 - 99,4%). Imprecision was estimated in accordance with manufacturer's claims. CONCLUSIONS: We obtained an overall sensitivity of 65,85% (95% CI 56,76-74,16%) and a specificity of 100% (95% CI 96,49-100%), slightly higher than the results reported by the manufacturer. Yet, it remains relatively low comparatively to what is generally acceptable for these antigenic assays (a relative sensitivity of 80%). We also noticed that the accuracy could reach its highest level if the cut-off is set above 0,673 which is lower than established by the manufacturer. Thus, our results suggest that the Elecsys® SARS-CoV-2 Antigen assays, should be improved prior to be used in a SARS-Cov-2 screening strategy. However, if one antigenic assay could demonstrate acceptable performance, it might be centralized in clinical laboratories, keeping the RT-PCR in a second phase for confirmation.

Use of the Cell-Dyn Sapphire hematology analyzer for automated counting of blood cells in body fluids.

The enumeration and identification of blood cells in body fluids offers important information for the diagnosis and treatment of various medical conditions. Manual microscopic methods (hemacytometer total cell count and cytocentrifuged differential count) have inherent analytic and economic disadvantages but are still considered the "gold standard" methods. We evaluated the analytic and clinical performance of the Cell-Dyn Sapphire hematology analyzer (Abbott Diagnostics Division, Santa Clara, CA) for automated blood cell counting and leukocyte differential counting in cerebrospinal fluid, serous fluid (peritoneal and pleural fluid), and continuous ambulatory peritoneal dialysis fluid, and we compared the performance with the respective manual methods. In the present article, we describe its applicability for the distinct body fluids, and we highlight limitations and caveats.

Evaluation of Sysmex UF-1000i for use in cerebrospinal fluid analysis.

BACKGROUND: Caution is of paramount importance in the interpretation of flow cytometric white blood cell counts in specimens with a high lymphocyte percentage as it is in the interpretation of bacterial counts in hemorrhagic and ventricular drainage CSF specimens. Recently, flow cytometry using a semiconductor laser along with forward and sideward scatter detection and also a dedicated bacterial channel has been developed (Sysmex UF-1000i). We explored the possible applications of this novel approach in the differential diagnosis of meningitis. METHODS: Flow cytometry, microscopy and biochemical data of 161 CSF samples were analyzed. Microbiological analysis was performed in 53 suspected cases of meningitis. RESULTS: Good agreement for leukocytes was obtained between UF-1000i (rho=0.614) and UF-100 (rho=0.582) and microscopy and between both flow cytometers (rho=0.734). Lymphocytes were correctly classified as WBC by UF-1000i. Bacterial count on UF-1000i showed to be reliable in hemorrhagic samples and in samples collected by ventricular drainage for which interference by blood platelets and cell debris forms a known caveat on UF-100. Bacterial background signal in sterile CSF samples was absent on UF-1000i. One case of Cryptococcus neoformans meningitis, missed by UF-100 was properly detected by UF-1000i. CONCLUSION: Sysmex UF-1000i CSF flow cytometer offers the clinician an improved aid in directing the differential diagnosis of meningitis towards viral, bacterial or fungal causes.

Serum hormones for predicting pregnancy outcome after assisted reproductive technology.

Serum human chorionic gonadotrophin (HCG) in the second and third week after embryo transfer has been used for prediction of pregnancy outcome after assisted reproduction. There are few data on the clinical utility of HCG, progesterone and oestradiol, measured by contemporary immunoassay, in the fourth week after embryo transfer and later. Moreover, large inter-method differences have been described between automated immunoassays, making method-specific cut-off values mandatory. The main aim of this study was to determine assay-specific optimal cut-off values for serum HCG, progesterone and oestradiol for prediction of clinical pregnancy outcome in singleton pregnancies after assisted reproductive techniques, at days 11, 18 and 25 and at week 6 after embryo transfer. A retrospective study was performed on frozen serum samples of 67 singleton pregnancies after assisted reproduction techniques. HCG, oestradiol and progesterone were determined with the automated (random access) VIDAS immunoanalyser. Receiver operating characteristic curve analysis was performed to determine optimal cut-off values. Predictive values were calculated based on the prevalence of non-viable pregnancy after assisted reproduction. It was concluded that measurement of HCG by VIDAS at days 18 and 25, and at week 6 after embryo transfer yields high positive (70.5-100%) and negative (87.2-94.4%) predictive values for clinical pregnancy outcome.