Application of commercial calibrators for the analysis of immunosuppressant drugs in whole blood.

low, particularly when it is 0.6, the dispersion of values for any individual will span only a small part of the reference interval. Reference values will thus be of little use, in particular for deciding whether a significant change has occurred. Conversely, when the index is high, particularly when it is 1.4, values from a single individual will cover much of the entire distribution of the reference interval. In this context, reference values will be of significant value for clinical interpretation. For total CoQ10, the index of individuality is 12.2/29.0 0.42; thus, it is low. In conclusion, we have derived data for the biological variation of CoQ10 together with reference values for the New Zealand population. The low index of individuality for CoQ10 indicates that individual CoQ10 concentrations are tightly distributed around a homeostatic setpoint and that significant changes can occur within the reference interval. From a statistical perspective, seven samples should be evaluated to ensure that the estimate of the homeostatic setpoint is within 10% of the true value, with 95% probability (15 ). From a clinical perspective, serial changes in CoQ10 should be evaluated against the RCV to allow for both biological variation and analytical imprecision.