İ ALTUĞLU, D. GÜRSEL, A. AKSOY, M ORMAN, S. ERENSOY

The importance and role of anti-HCV signal/cutoff ratio in diagnosis of hepatitis C virus infection

Different signal/cutoff values for different commercial kits are used to determine the samples that would predict a true antibody response for Hepatitis C Virus infection. The aim of this study is to determine a specific signal/cutoff ratio with the commercial kit that is used routinely in our laboratory that would predict a true antibody positive result 95% of the time regardless of the anti-HCV prevalance. Material and Methods: A total number of 309 anti-HCV positive samples that were tested with the architect anti-HCV assay (Abbott Laboratories, IL, USA) were reviewed retrospectively and categorized according to their signal/cutoff ratio. These samples were retested with LIA (Innogenetics N.V., Belgium). ROC-curve analysis in SPSS 17.0 statistical package programme was used for data analysis. Results: The signal/cutoff ratio 3.27 is determined as the cutoff point that predicts a true antibody positive result in 94.9% (positive predictive value 94.9 %, specificity 81.4%, sensitivity 91.2%) of the cases according to the ROC curve analysis. Conclusion: A stepwise approach is appropriate for evaluation of patients positive for anti-HCV. It is important for laboratories to determine a cutoff point to distinguish between a low and high positive Anti-HCV result. With the architect anti-HCV assay (Abbott, USA), in cases with signal/cutoff >3.27, the line immunoassay will be positive in most patients, so supplementary testing in such individuals is not needed.

Anti-HCV sinyal/eşik değer oranının Hepatit C virüs enfeksiyonu tanısında rolü ve önemi

Amaç: Hepatit C virüs enfeksiyonunda farklı ticari kitler ile gerçek antikor pozitifliğini öngören farklı Anti-HCV sinyal/eşik değer oranları belirlenmiştir. Bu çalışmanın amacı, laboratuvarımızda rutin olarak kullanılan ticari kit için anti-HCV prevalansından bağımsız olarak %95 gerçek antikor olumluluğunu öngören spesifik bir sinyal/eşik değer oranı belirlemektir. Gereç ve Yöntem: Architect anti-HCV (Abbott Laboratories, IL, ABD) kiti ile daha önce test edilen 309 anti-HCV pozitif örnek sinyal/eşik değerlerine göre sınıflandırıldı. Bu örnekler LIA (Innogenetics N.V., Belçika) ile tekrar test edildi. Veri analizi için 17.0 SPSS paket programındaki ROC eğri analizi kullanıldı. Bulgular: ROC eğrisi analizine göre 3.27 sinyal/eşik değer oranı, gerçek antikor pozitifliğini öngören eşik değer olarak bulundu (pozitif prediktif değer %94.9, özgüllük %81.4, duyarlılık %91.2). Sonuç: Anti-HCV pozitif bulunan hastaların değerlendirilmesinde basamaklı bir yaklaşım uygundur. Laboratuvarların, düşük ve yüksek anti-HCV pozitifliğini ayırt edebilecek bir eşik değer belirlemesi önemlidir. Architect anti-HCV testi (Abbott, ABD) ile sinyal/eşik değeri >3.27 olan örneklerde line immunoassay testi hastaların çoğunda pozitif olarak bulunacağından, bu hastalarda bu tip bir destekleme testinin uygulanmasına gerek yoktur.

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