Analytical goals for the acceptance of common reference intervals for laboratories throughout a geographical area

Abstract

Analytical goals required for the successful transfer of reference intervals between laboratories within a specified limited geographical area, with a population homogeneous for the quantities, are presented. Diagrams are shown which allow the investigation of the influence of analytical imprecision and bias, both separately and in combination, on the percentage of the population outside each reference limit. Figures to evaluate the effect of population sample size on the size of confidence interval around each reference limit are combined with the diagrams for analytical imprecision and bias. The maximum acceptable percentage of the population outside the limit for the 0.90 confidence interval of each of the x±1.96 s reference limits is 4.6% for a population sample size of 120. Based on this, the maximum acceptable imprecision, with no bias, is 0.6 of the total biological standard deviation (s_B) and the maximum acceptable bias, with no imprecision, is 0.25 s_B.

Key Words:

• analytical bias
• analytical imprecision
• biological standard deviation
• confidence intervals
• Gaussian distribution
• percentage of population outside reference limits
• probit transformation