It is rare to get the same results when a sample of the individual is measured at different times, even if the state of health in the individual has not been changed. If such difference in test results from repeated testing is observed, physicians and health care professionals should also be aware of possible factors other than laboratory error.
When a sample of an individual is measured at different times at the same or different clinical laboratory, the results are always different, even the state of health of an individual is the same. This
disparity in the results from clinical laboratories might confuse diagnosing, treating, and monitoring disease. Patients and healthcare professionals usually interpret these differences as laboratory errors.
However, this might not always be the case, because laboratory test results are highly variable and are neither consistent nor comparable due to several reasons other than laboratory error, namely preanalytical variation, biological variation, and analytical variation.