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Turkish Journal of Biochemistry

Türk Biyokimya Dergisi


IMPACT FACTOR 2018: 0.329

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1303-829X
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Volume 41, Issue 6

Issues

Diagnostic pitfall of carryover: in automatic urine analyzers

İdrar otoanalizörlerinde bulaşmanın diagnostik tuzağı

Eren Vurgun
  • Corresponding author
  • Okmeydani Training and Research Hospital – Department of Medical Biochemistry, Istanbul, Turkey
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  • De Gruyter OnlineGoogle Scholar
/ Osman Evliyaoğlu
  • Okmeydani Training and Research Hospital – Department of Medical Biochemistry, Istanbul, Turkey
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  • De Gruyter OnlineGoogle Scholar
/ Sembol Yıldırmak
  • Giresun University Faculty of Medicine – Department of Medical Biochemistry, Giresun, Turkey
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  • De Gruyter OnlineGoogle Scholar
/ İbrahim Akarsubaşı
  • Gaziosmanpasa Taksim Training and Research Hospital – Department of Medical Biochemistry, Istanbul, Turkey
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
Published Online: 2016-11-02 | DOI: https://doi.org/10.1515/tjb-2016-0162

Abstract

Objective:

We aimed to find out whether there is significant carryover effect which causes false-positive hematuria on red blood cells (RBCs) in automatic urine chemistry (DIRUI H-800) and sediment (DIRUI FUS-200) analyzers.

Methods:

Twenty-four samples with gross hematuria selected as containing high RBC concentration and forty-eight samples which had both negative result in dipstick and 0/hpf in microscopic examination selected as containing low RBC concentration. Carryover% was calculated via the formula [carryover%=100×(b1−b2)/(a2−b2)]. Carryover effect within results was analyzed with Wilcoxon test.

Results:

Carryover% was very high (67%) in urine chemistry analyzer. Carryover% of urine sediment analyzer was found 0.4% whilst false-positive hematuria percentage was 87.5% for the first samples came after gross hematuria and 6.6% for the second samples. The first samples analyzed after gross hematuria had significantly higher (p<0.001) results than the second samples in both analyzers.

Conclusion:

In urine sediment analyzer, carryover% calculated by formula was found analytically sufficient, but it causes highly false-positive results due to diagnostic limit of hematuria (RBC>3/hpf) is low. To prevent carryover in both urine analyzers; washing procedures should be revised and the diagnostic effect of carryover should also be taken into account by biochemists.

Özet

Amaç:

Laboratuvarımızda kullanılan idrar otoanalizöründe örneklerin kimyasal ve sediment analizinde, analitik olarak kabul edilebilir sınırda olmasına rağmen yanlış pozitif hematüri tanısına yol açabilecek eritrosit bulaşması olup olmadığını tespit etmeyi amaçladık.

Metod:

Hasta örneklerinden 24 adet makroskopik hematürili ve 48 adet eritrosit içermeyen idrar numunesi seçildi. Eritrosit içermeyen örnekler, makroskopik hematürili örneklerin ardından tekrar analiz edildi. Bulaşma yüzdesi Broughton’un formülü [carryover%=100× (b1−b2)/(a2−b2)] ile hesaplandı. Bulaşma etkisinin sonuçları etkileyip etkilemediği Wilcoxon testi ile değerlendirildi.

Bulgular:

İdrar kimyasal analizöründeki bulaşma %67 oranında iken sediment analizinde ise %0,4 olarak bulundu. İdrar sediment analizöründe eritrosit içermeyen örneklerin yanlış pozitiflik oranlarının hematüriden sonra çalışılan 1.örneklerde %87,5, 2.örneklerde ise %6,6 olduğu belirlendi. Her iki analizörde de hematüriden sonra gelen 1.örneklerin sonuçları, 2.örneklerin sonuçlarından istatistiksel olarak anlamlı yüksek bulundu (p<0.001).

Sonuç:

İdrar sediment analizöründeki bulaşma yüzdesi, analitik performans sınırı olarak kabul edilen %1 değerinin altında olmasına rağmen; bu bulaşma yüzdesinin hematürinin diagnostik sınırının düşük olması (RBC>3/hpf) nedeniyle, yüksek oranda yanlış pozitif hematüri sonuçlarına neden olduğu saptandı. Bulaşmayı önlemek için, her iki idrar analizörünün de yıkama basamakları ve prosedürleri revize edilmelidir. Ayrıca biyokimya uzmanları, bulaşmanın analitik sınırları ile birlikte olası tanısal etkilerine de gerekli dikkati göstermelidir.

Keywords: Carryover; Carryover effect; False-positive hematuria; Automatic urine analyzer; Diagnostic

Anahtar kelimeler:: Bulaşma; Bulaşma etkisi; Yanlı ş-pozitif hematüri; Idrar otoanalizörü; Diagnostik

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About the article

Received: 2015-09-03

Accepted: 2016-05-02

Published Online: 2016-11-02

Published in Print: 2016-12-01


Conflict of interest statement: There are no conflicts of interest among the authors.


Citation Information: Turkish Journal of Biochemistry, Volume 41, Issue 6, Pages 473–478, ISSN (Online) 1303-829X, ISSN (Print) 0250-4685, DOI: https://doi.org/10.1515/tjb-2016-0162.

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