Rapid Antigen Testing in the Diagnosis of COVID-19: Verification and Algorithm Experience

Abstract

Aim: Rapid antigen tests (RATs) for the diagnosis of SARS-CoV-2 are increasingly being used for the early detection of symptomatic cases and interruption of transmission chains. In our study, the impact of transporting upper respiratory tract swab samples in transfer tubes containing protective liquid (vNAT) or in sterile bags without vNAT on the detection of SARS-CoV-2 by RT-PCR and rapid antigen tests was evaluated.

Material and Methods: Nasopharyngeal/oropharyngeal swab samples from 200 patients were included in our study. Two samples were collected from each patient using a disposable swab; one sample was placed in a transfer tube containing vNAT, while the other was placed in a sterile locked bag and tested with the SARS-CoV-2 rapid antigen test. The results were then compared with PCR results, and CT values were analyzed in terms of the algorithm.

Results: RT-PCR was positive in 68 out of 200 patients, with Ct values ranging from 16.4 to 29.49 and an average Ct value of 23.08. Swab samples without vNAT from these 68 patients were evaluated using antigen tests, and 58 (85.3%) were positive. Additionally, the same rapid antigen tests performed with swab samples placed in vNAT detected 49 (72%) positive cases.

Conclusion: In our study, it was revealed that performing RATs from samples taken for PCR tests and transported with vNAT was a factor reducing the sensitivity. Rapid antigen tests are the most important alternatives to PCR tests in the rapid detection of symptomatic cases and breaking the chain of transmission, if the selection of the test, sample collection/transport and performing the test are in an appropriate algorithm. “Correct test selection” and “correct test algorithm” are vital for the pandemic to be brought under control.

Keywords

• COVID-19
• SARS CoV-2
• rapid antigen tests
• Ct
• vNAT transfer medium

COVID-19 Tanısında Hızlı Antijen Testleri: Doğrulama ve Algoritma Deneyimi

Abstract

Amaç: Semptomatik vakaların hızlı tespiti ve bulaş zincirinin kırılması amacıyla SARS-CoV-2 tanısında hızlı antijen testleri (RAT) giderek daha fazla kullanılmaktadır. Çalışmamızda, üst solunum yolu sürüntü örneklerinin viral nükleik asit tamponu(vNAT) içeren taşıma tüplerinde veya vNAT içermeyen steril poşetlerde taşınmasının, RT-PCR ve hızlı antijen testleri ile SARS-CoV-2 saptanmasına etkisi değerlendirilmiştir.

Gereç ve Yöntemler: Çalışmamıza 200 hastadan alınan nazofarengeal/orofarengeal sürüntü örnekleri dahil edilmiştir. Her hastadan tek kullanımlık sürüntü çubuğuyla iki örnek alınmış; bir örnek vNAT içeren taşıma tüpüne, diğer örnek ise steril kilitli poşete yerleştirilmiş ve SARS-CoV-2 hızlı antijen testi ile test edilmiştir. Elde edilen sonuçlar PCR test sonuçlarıyla karşılaştırılmış ve eşik döngüsü (CT) değerleri algoritma açısından analiz edilmiştir.

Bulgular: 200 hastanın 68’inde RT-PCR pozitif saptanmış; Ct değerleri 16,4 ile 29,49 arasında değişmiş ve ortalama Ct değeri 23,08 olarak bulunmuştur. Bu 68 hastadan vNAT içermeyen örneklerle yapılan antijen testlerinde 58’i (%85,3) pozitif saptanmıştır. Aynı hızlı antijen testleri vNAT içeren örneklerle yapıldığında ise 49’u (%72) pozitif bulunmuştur.

Sonuç: Çalışmamızda, PCR için alınan ve vNAT ile taşınan örneklerden yapılan RAT’ların, testin duyarlılığını azalttığı ortaya konmuştur. Uygun test seçimi, örnek alımı/taşınması ve testin uygun algoritmaya göre uygulanması durumunda, hızlı antijen testleri semptomatik vakaların hızlı tespiti ve bulaş zincirinin kırılmasında PCR testlerine en önemli alternatiftir. “Doğru test seçimi” ve “doğru test algoritması” pandeminin kontrol altına alınmasında hayati öneme sahiptir.

Keywords

• COVID-19
• SARS-CoV-2
• hızlı antijen testleri
• Ct
• vNAT taşıma ortamı

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