J Korean Med Sci.  2018 Mar;33(10):e81. 10.3346/jkms.2018.33.e81.

Effect of the Standardization of Diagnostic Tests on the Prevalence of Diabetes Mellitus and Impaired Fasting Glucose

Affiliations
  • 1Department of Biostatistics, Clinical Trial Center, Soonchunhyang University Bucheon Hospital, Soonchunhyang University College of Medicine, Bucheon, Korea.
  • 2Clinical Trial Center, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.
  • 3Department of Laboratory Medicine and Genetics, Soonchunhyang University Bucheon Hospital, Soonchunhyang University College of Medicine, Bucheon, Korea. cecilia@schmc.ac.kr
  • 4Department of Laboratory Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.
  • 5Department of Laboratory Medicine, Yonsei University College of Medicine, Seoul, Korea.
  • 6Department of Laboratory Medicine, Ajou University School of Medicine, Suwon, Korea.
  • 7Department of Laboratory Medicine, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.
  • 8Department of Biostatistics, Korea University College of Medicine, Seoul, Korea.

Abstract

BACKGROUND
Without standardization of medical laboratory's testing practices, there is an increase in false diagnoses when relying on test results. However, the effect of test standardization is difficult to assess numerically. This study's purpose is to quantify the effect of the standardization level of a laboratory on the prevalence of diabetes mellitus (DM) and impaired fasting glucose (IFG).
METHODS
Laboratories were classified into three levels: "˜highly-standardized laboratory,'"˜basically-standardized laboratory,' and "˜non-standardized laboratory.' Based on the results of Korean External Quality Assessment Scheme (KEQAS), the cutoff values for diagnosis of DM and IFG were recalculated, given false positive and false negative rates.
RESULTS
The prevalence of DM and IFG in the population as a whole was estimated using the 2013 Korea National Health and Nutrition Examination Survey (KNHANES) database. When the prevalence of DM from KNHANES was 11.88% (95% confidence interval [CI], 10.59%-13.17%), the proportion with a systematic false error ranged from 10.91% (95% CI, 9.65%-12.17%) to 13.09% (95% CI, 11.74%-14.45%). The prevalence of IFG varied from 13.59% (95% CI, 12.25%-14.91%) to 40.49% (95% CI, 38.54%-42.43%), in contrast to 24.58% (95% CI, 22.85%-26.31%) of the reference value. The prevalence of DM and IFG tended to be over- and under-estimated more as the laboratory standardization level became lower, respectively.
CONCLUSION
Our study proved that standardization of clinical laboratory tests is an important factor affecting the prevalence estimation of national disease statistics based on the simulation using KNHANES data.

Keyword

Standardization of Diagnostic Tests; Korean External Quality Assessment Scheme; Variance Index Score; National Prevalence; False Positivity; False Negativity
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