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Published reference change values (RCVs), often fixed percentages, may inaccurately assess clinical significance of analyte changes. Using RCVs as a function of the first result improves diagnostic accuracy for laboratory testing.

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Area of Science:

  • Clinical Chemistry
  • Laboratory Medicine
  • Biostatistics

Background:

  • Reference change values (RCVs) help physicians interpret serial laboratory test results.
  • Published RCVs typically use fixed percentages of the initial value, but their accuracy is uncertain.

Purpose of the Study:

  • To evaluate the accuracy of fixed-percentage RCVs for common analytes.
  • To compare published RCVs with empirical percentiles derived from large population data.

Main Methods:

  • Utilized US National Health and Nutrition Examination Survey (NHANES) 2001-2002 data.
  • Analyzed changes in eight analytes (albumin, calcium, cholesterol, etc.) in individuals with stable concentrations.
  • Calculated RCVs using biological and analytical variation, comparing them to empirical data.

Main Results:

  • Fixed-percentage RCVs showed variable sensitivity (0.35 for sodium to 0.80 for albumin) and specificity (0.85 for potassium to 0.97 for thrombocytes).
  • Calculating RCVs as fixed percentages reduced diagnostic accuracy.
  • RCVs dependent on the initial result demonstrated superior performance.

Conclusions:

  • Fixed-percentage RCVs may not reliably detect clinically significant analyte changes.
  • A model where RCVs are a function of the initial result offers improved diagnostic accuracy.
  • Future RCV calculations should consider results-dependent methodologies.