Westgardregels

Westgardregels, also known as Westgard Rules, are a set of statistical criteria used in clinical laboratories to monitor and evaluate the quality of analytical testing procedures. Developed by James O. Westgard in the 1970s, these rules serve as guidelines for identifying when an analytical run may be compromised by systematic or random errors, prompting further investigation or corrective actions.

The rules are applied to control charts, particularly Levey-Jennings charts, which plot control sample measurements over time. Westgard namely established a series of multi-rule combinations that specify acceptable ranges for control measurements, typically expressed in terms of standard deviations (sigma) from a target value. Commonly used rules include the "1-2s" rule (one point exceeds 2 sigma limits), "1-3s" (one point exceeds 3 sigma limits), "2-2s" (two consecutive points exceed 2 sigma on the same side), "R-4s" (two consecutive points exceed ±2 sigma in opposite directions), and "4-1s" (four consecutive points exceed 1 sigma on the same side).

Applying these rules allows laboratories to detect trends, shifts, or random errors promptly, maintaining the accuracy and reliability of test results. The implementation of Westgard rules is integral to quality control protocols in clinical laboratories, ensuring compliance with regulatory standards and safeguarding patient safety through consistent test performance. Over time, these rules have become a standard part of laboratory quality assurance programs worldwide, contributing significantly to the field of laboratory diagnostics.