Naslov
Limit of detection (LoD) of SARS-CoV-2 using RT- qPCR with an commercial kit - retesting needed or not?

Autori
Kardum Paro, Mirjana Mariana ; Tkalčić Švabek, Željka ; Horvat, Martina ; Parašilovac, Nikolina

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Poster Abstracts. U: Clinical Chemistry and Laboratory Medicine (CCLM), 61(S1) / - : Walter de Gruyter, 2023, S746-S746

Skup
WorldLab-EuroMedLab Roma 2023

Mjesto i datum
Rim, Italija, 21.05.2023. - 25.05.2023

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
SARS-CoV-2 ; limit of detection (LoD)

Sažetak
BACKGROUND-AIM. Real-time reverse transcriptase- polymerase chain reaction (RT-qPCR) is current the gold standard for qualitative detection of SARS- CoV-2 in nasopharyngeal (NP) and/or oropharyngeal (OP) swabs. Aim of the study was to determine proper limit of detection (LoD) and base treshold value (Ct value) to correctly distinguish positive from negative SARSCoV-2 results. METHODS. In 2022 RT-qPCR (SARS-CoV-2 kit Sacace/ABI 7500 Real Time), accredited according ISO15189 standard, was performed after RNA isolation (ExiPrep 96 Viral DNA/RNA Kit/ExiPrep96 Lite, Bioneer) from 17240 NP/OP swabs. Manufacturers LoD (10 copies/PCR ; 50 µl eluate) with Ct value 32, 0 for all determinated (E-like/ E/ N) genes was confirmed by manufacturers positive sample dilution (1:100, unknown RNA copy number), while determinated LoD (750 copies/mL) with genes Ct values 32, 4 (E- like), 32, 7 (E) and 32, 6 (N) was proven by positive sample dilution (1:1000/AmpliRUN RNA CTRL, Vircell/15000 copies/ µl) with NP/OP negative samples and detection rate > 0.95%. SARS- CoV-2 results were considered positive (all Ct values < 32, 4), negative (all Ct values > 32, 7) or marginal (at least one 32, 4 < Ct value < 32, 7). RESULTS. From 17240 NP/OP swabs, 6135 were positive (35, 6%) and 11049 negative (64, 1%). 56 patients (0, 3%) with marginal SARS-CoV-2 results were counseled to retest after 24/48 hours because of the Ct value(s) at the determinated LoD (Ct 32- 33). 37 patients did not retest (66%), 19 retested (34%) and 10 of 19 retested (53%) considered SARS- CoV-2 positive (Ct 15-32). CONCLUSIONS. As shown, marginal SARS-CoV-2 results can be considered presumptive positive SARS-CoV-2 results. Retesting may be helpful if early stage disease is present and viral RNA levels are still low. Proper determination of LoD is a key criteria for routine qualitative detection of SARS-CoV-2, small number of retested samples and correct distinction positive from negative SARS-CoV-2 results.

Izvorni jezik
Engleski

Znanstvena područja
Kliničke medicinske znanosti

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