SARS-CoV-2 Enfeksiyonunun Mikrobiyolojik Tanısı

Abstract

Aralık 2019’da Çin’den başlayarak çok kısa bir süre içerisinde tüm dünyayı etkisi altına alan Coronavirus Disease 2019 (COVID-19) pandemisi, bugüne kadar görülen en ciddi küresel sağlık sorunlarından biri haline gelmiştir. Bu süreçte, zamanında ve doğru uygulanan mikrobiyolojik tanı testleri, salgının ve vaka yönetiminin önemli bir parçası olmuştur. Pandeminin başlangıcından itibaren solunum yolu örneklerinde severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA’sını saptamaya yönelik olarak geliştirilen gerçek zamanlı ters transkriptaz-polimeraz zincir reaksiyonu (RT-PCR), en yaygın kullanılan tanı yöntemidir. RT-PCR ile virüs RNA’sının gösterilmesi COVID-19 hastalığının kesin tanısını sağlamakla birlikte negatif test sonucu enfeksiyon olasılığını dışlamaz. Klinik şüpheli olgularda 24-48 saat arayla tekrarlayan örneklerin alınması ve ciddi akciğer bulguları olan hastalarda tanı için alt solunum yolu örneklerinin tercih edilmesi gereklidir. Düşük maliyetli, uygulanması kolay ve hızlı sonuç alınabilen antijen testlerinin kullanımı, viral yükün yüksek olduğu hastalığın akut evresi ile sınırlıdır. Duyarlılık ve özgüllük sorunlarından dolayı antijen testleriyle elde edilen sonuçların RT-PCR testleri ile doğrulanması gerekir. Antikor testleri, virüs ile karşılaşılmış olduğunu gösterir. Hastaların virüse karşı antikor yanıtının değişken ve geç olması nedeniyle antikor testleri, akut dönemde hastalığın tanısında tek başına kullanılmamalıdır. Semptomların başlangıcından 2-3 hafta sonra alınan kan örneklerinde çalışılan antikor testleri moleküler tanıya yardımcı ek test olarak kullanılabilir. Bu derlemede, günümüze kadar elde edilen veriler doğrultusunda SARS-CoV-2 enfeksiyonunun mikrobiyolojik tanısında kullanılan yöntemlerin özellikleri, klinik açıdan sağladıkları avantajlar ve kısıtlı yönleri tartışılmıştır.

Keywords

• COVID-19
• SARS-CoV-2
• polimeraz zincir reaksiyonu
• antijen testi
• antikor testi

Microbiological Diagnosis of SARS-CoV-2 Infection

Abstract

The Coronavirus Disease 2019 (COVID-19) pandemic, which began in China in December 2019 and affected the whole world in a very short time, has become one of the most serious global health problems to date. In this process, timely and correctly applied microbiological diagnostic tests have been an important part of the epidemic and case management. Since the beginning of the pandemic, real-time reverse transcriptase-polymerase chain reaction (RT-PCR), which has been developed to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA in respiratory tract samples, is the most widely used diagnostic method. The detection of the virus RNA by RT-PCR provides the definitive diagnosis of COVID-19 disease, but a negative test result does not exclude the possibility of infection. In clinically suspicious cases, repeated samples should be taken within 24-48 hours and lower respiratory tract samples should be preferred for diagnosis in patients with severe lung findings. The use of low-cost and easy-to-apply rapid antigen tests is limited to the acute phase of the disease when viral load is high. Due to sensitivity and specificity problems, the antigen test results should be confirmed by RT-PCR tests. Antibody tests indicate the exposure to the virus. Antibody tests should not be used alone in the diagnosis of the disease in acute phase, because the antibody response of the patients against the virus is variable and late. Antibody tests, which are performed on the blood samples taken 2-3 weeks after the onset of symptoms, can be used as an additional test to aid molecular diagnosis. In this review, the features, clinical advantages and limitations of the methods used in the microbiological diagnosis of SARS-CoV-2 infection are discussed in line with the obtained data to date.

Keywords

• COVID-19
• SARS-CoV-2
• polymerase chain reaction
• antigen test
• antibody test

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