Other Components of a QA Program Laboratory Operations Review 59
ACTIVITY EXPLANATION
Correlation study
Preventive maintenance
Function checks
Delta checks
Critical values
Study to verify accuracy of new method. Split patient samples are analyzed by existing method
& new method. Requires a minimum of 40 patient samples representing wide range of concen-
trations. Reference values (existing method) are plotted on xaxis, values from new method
on yaxis. Perfect correlation is straight line passing through zero at 45ºangle. The correlation
coefficient (r) can be derived mathematically. Values range from −1 to +1. 0 = no correlation
between methods. +1 = perfect direct correlation. ≥0.95 = excellent correlation.Schedule of maintenance to keep equipment in peak operating condition. Maintenance must
be documented & must follow manufacturer’s specifications & frequencies.Procedures specified by manufacturer to evaluate critical operating characteristics of test
system, e.g., stray light, background counts. Must be within manufacturer’s established limits
before patient testing is conducted. Documentation required.Comparison of patient data with previous results. Detects specimen mix-up & other errors.
When limit is exceeded, must determine if due to medical change in patient or lab error.Test results that indicate a potentially life-threatening situation. List typically includes glucose,
Na+, K+, total CO 2 , Ca2+, Mg2+, phosphorus, total bili (neonates), blood gases. Patient care per-
sonnel must be notified immediately. The Joint Commission requires “read-back” policy. Person
receiving critical values must record & read back patient’s name & critical values. Lab must
document person who received information & time of notification.continued...