Figure 6. Sources of lab test variability.

Percent of the variability explained by each component of the LMM (testing service, subject, blood collection time, and “other”, i.e., residuals, unexplained by other covariates). Subject variability — not shown explicitly — makes up the remaining difference from 100% (e.g., MCHC = 23%, hs-CRP = 98%). The interservice variability can also be interpreted in terms of the intraclass correlation. For example, consider the lab test for MCHC. Variation across testing service explains 65% of the overall observed variance. This result is equivalent to saying that, after correcting for the effects of subject and collection time, the correlation between samples from different services is 65%.