Journal of Veterinary Clinics (한국임상수의학회지)

The Korean Society of Veterinary Clinics (한국임상수의학회)
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Prevalence-based Interpretation of Predictive Values of Diagnostic Tests: An Example for Detection of Canine Heartworm Infection

진단키트 검사결과에 대한 유병율 위주 해석: 개 심장사상충의 예

  • Park, Choi-Kyu (School of Veterinary Medicine and Institute of Veterinary Science, Kangwon National University) ;
  • Pak, Son-Il (National Veterinary Research and Quarantine Service)
  • 박최규 (강원대학교 수의학부(대학) 및 동물의학연구소) ;
  • 박선일 (국립수의과학검역원)
  • Published : 2009.04.30
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Abstract

The use of screening tests as part of a diagnostic work-up is common in domestic canine practice, but understanding of the diagnostic test characteristics and factors affecting diagnostic accuracy is not clear among clinicians. This article was aimed to provide clinicians with a better understanding on the selection of test kits and with a proper interpretation of test results using an example from heartworm(Dirofilaria immitis) studies. From the literatures, diagnostic accuracy varied depending on the kits: percent average sensitivity and specificity of ELISA antigen-detecting kits were DiroChek(Synbiotics, USA) 78.1 and 95.2, SNAP(IDEXX, USA) 66.3 and 98.1, and Solo Step(Heska, Switzerland) 69.5 and 97.5, respectively, while the values for three hematological methods(Modified Knott's, direct smear and capillary tube) ranged from 38.4 to 81.8% and from 96.9 to 100%, respectively. Furthermore, it was also reported that the prevalence of heartworm disease in domestic dog populations varied depending on the regions studied: 2.5-22.8% for microfilarial test and 2.2-66.3% by ELISA. The values of predictive values for positive(PPV) and negative(NPV) provide useful information to clinicians on the probability of heartworm infection, but the PPV and NPV are greatly dependent on the heartworm prevalence. This suggests that PPV or NPV values of a test should be interpreted carefully in different clinical settings. Practical methods on the interpretation taking into account heartworm prevalence were discussed.

검사키트의 신속성과 간편성이 보편화되면서 진단목적으로 키트를 사용하는 빈도가 증가하고 있다. 그러나 대부분의 검사키트는 민감도와 특이도가 100% 완벽하지 못하기 때문에 진단검사의 특성과 이러한 특성에 영향을 미치는 요인을 이해하지 못할 경우 검사결과를 해석하는데 오류를 범하게 된다. 임상의는 검사결과 양성 혹은 음성일 때 환자가 실제로 질병에 감염되어 있을 확률이 어느 정도인지에 관심을 두기 때문에 본 연구에서는 예측도를 이용하여 유병율에 따른 결과 해석방법을 개 심장사상충 진단키트를 예로 들어 설명하였다. 문헌고찰 결과 심장사상충 진단용 키트검사의 평균 민감도와 특이도는 DiroChek 78.1-95.2%, SNAP 66.3-98.1%, Solo Step 69.5-97.5%를 보였다. 혈액학적 검사법(Modified Knott's, direct smear, capillary tube)의 민감도와 특이도는 각각 38.4-81.8%, 96.9-100%의 범위를 보여 검사법에 따라 상당한 차이를 보였다. 또한 국내 개 심장상충의 자충과 항원 유병율은 지역별로 차이가 있으며 키트검사의 예측도는 유병율에 매우 민감하다는 점을 고려하면 개 심장사상충에 대한 검사결과에 근거하여 감염확률을 추정할 때 유병율이 상이한 임상환경에서는 양성 혹은 음성결과에 대하여 신중하게 해석할 필요가 있다.

Keywords

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