KLİNİK ÖRNEKLERDEN MYCOBACTERIUM TUBERCULOSIS KOMPLEKS TANISINDA MTD (GEN-PROBE) SONUÇLARININ DEĞERLENDİRİLMESİ

Öz

Bu çalışmada, pulmoner ve ekstrapulmoner örneklerden MTD (Mycobacterium tuberculosis direct test) (Gen-Probe, Inc. San Diego, A.B.D.) testi ile Mycobacterium tuberculosis kompleks (MTB) moleküler tanısının kültür sonuçları ve klinik veri ile karşılaştırılarak duyarlılık ve özgüllüğünün retrospektif olarak değerlendirilmesi amaçlandı. Hastanemiz mikrobiyoloji laboratuvarına Temmuz 2004 ve Mayıs 2005 tarihleri arasında kabul edilen toplam 764 örnek (%84 pulmoner ve %16 ekstrapulmoner) çalışmaya alındı. Tüm örneklere asido-rezistan boyama, kültür ve MTD uygulandı. MTD sonuçları üretici firma önerileri doğrultusunda değerlendirildi. 30.000 ve 499.999 RLU arasındaki değerler kuşkulu sınır olarak düşünüldü ve tüm kuşkulu sonuçlar için test yinelendi. Uyumsuz sonuçlar, klinik veri ve örneklerin yinelenen sonuçları ile beraber değerlendirildi. MTD, kültür ve yayma pozitifliği, sırasıyla, %19.1, %17.7 ve %4.3 olarak bulundu. Dört örneğin MTD sonucu kuşkulu sınır olarak saptandı. Altı örneğin kültür sonucu kontaminasyon ve dört örnek ise atipik mikobakteri olarak belirlendi. Genel olarak, örnekler için duyarlılık, özgüllük, pozitif ve negatif prediktif değerler sırasıyla, %94.1, %99.1, %99.2 ve %99.5 olarak bulundu. Pulmoner, ekstrapul-moner, yayma pozitif ve yayma negatif örnekler için duyarlılık, sırasıyla, %93.8, %80, %100 ve %91.7 olarak hesaplandı. Hem ekstrapulmoner ve hem de pulmoner örneklerin özgüllüğü %99.1 olarak bulundu. Kültür ve yayma ile negatif ve MTD ile pozitif bulunan 13 örnek, klinik veri ile tüberküloz olarak değerlendirildi. Sonuç olarak, nükleik asit amplifikasyon temelli MTD testi, klinik örneklerden MTB'in hızlı tanısında güvenilir olmakla birlikte, seçilmiş hastalarda, klinik veriler ve geleneksel tanı yöntemleri ile beraber yorumlanarak kullanılması gerektiği düşünüldü.

Anahtar Kelimeler

• Tüberküloz, MTD, Gen-Probe, moleküler tanı

EVALUATION OF MTD (GEN-PROBE) RESULTS FOR DIRECT DETECTION OF MYCOBACTERIUM TUBERCULOSIS COMPLEX IN CLINICAL SPECIMENS

Abstract

Evaluation of sensitivity and specificity of the molecular detection of Mycobacterium tuberculosis complex (MTB) by MTD (Gen-Probe, Inc., USA) for diagnosis of tuberculosis in comparison with culture results and clinical outcome was intended. A total of 764 specimens submitted to the microbiology lab of our hospital between July 2004 and May 2005 were studied. Acid-fast staining, culture and MTD were performed on all samples. Among the specimens, 84% and 16% of them were pulmonary and extrapulmonary specimens, respectively. MTD results were interpreted according to the manufacturer's recommendations. The values between 30,000 and 499,999 RLU were considered as indeterminate. All indeterminate results were repeated twice. Resolution of discordant results was accomplished by incorporating clinical data and repeated specimen analysis. MTD, culture and smear positivity were 19.1%, 17.7% and 4.3%, respectively. MTD results for four specimens were indeterminate. Six of culture results were contaminated and four of them were identified as atypical mycobacterium. Overall sensitivity, specifity, positive and negative predictive values for the specimens were found as 94.1%, 99.1% 99.2% and 99.5%. Sensitivity for pulmonary, extrapulmonary, smear positive and smear negative specimens were 93.8%, 80%, 100% and 91.7%, respectively. Specifities for extrapulmonary and pulmonary specimens were found as 99.1% for each. Thirteen MTD positive specimens which were found as negative with culture and smear were diagnosed as tuberculosis by incorporating clinical data. In conclusion, MTD test can be used as a rapid, reliable and accurate detection of MTB in clinical specimens. However, MTD should be used in selected patients and should be interpreted in accordance with the clinical outcome and conventional diagnostic techniques.

Keywords

• Tuberculosis, MTD, Gen-Probe, molecular detection

Kaynakça

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