Westgard Rules

Westgard rules are multi-rule quality control for clinical laboratories. Control material of known value is run alongside patient samples, and the result is judged against the historical mean and standard deviation for that control and instrument. Rules are written in a shorthand — 1-3s for a single point beyond three standard deviations, 2-2s for two consecutive beyond two, 10x for ten consecutive on one side of the mean — and a breach means the run is questioned before results are released.

Why it matters in a hospital

A laboratory can be precise and still be wrong: an analyser drifting steadily in one direction produces beautifully consistent results that are all shifted. Single-point rules never catch that, which is why the multi-point rules exist — they look at the series rather than the reading. The corollary matters operationally: judging a control run against one value silently collapses full Westgard to its weakest rule while still looking like quality control.

How Trisvio handles it

Trisvio evaluates control runs against the historical series for that device and lot, and can refuse clinical verification of a result when the most recent in-window control for the device and analyte was rejected — naming the device, the analyte and the failing run. It deliberately does not block where there is no QC at all, or for a manually entered result with no instrument behind it, because a gate that over-blocks gets switched off and then protects nothing.