Abstract
Clinical laboratory tests are essential for diagnosing diseases, monitoring therapeutic regimens, and determining the prognosis of patients in daily clinical practice. However, before interpreting test results for any such purpose, we need to consider the possible sources of variation (SVs) other than those caused by pathological processes. Nonpathological SVs include biological (physiological) sources of variation (BSVs) and analytical sources of variation (ASVs). BSVs are divided into interindividual SVs, such as age, gender, environment, lifestyle, and genetics, and intraindividual SVs, which affect sampling conditions, such as posture, physical activities, and time of day. In this review article, the effects of interindividual SVs, namely, age, gender, obesity, and habits of smoking and drinking, and those of intraindividual SVs, namely, posture, physical exercise, diurnal rhythm, and short-term effects of smoking and drinking, on test results are discussed systematically on the basis of the authors’ experiences. All lines of evidence on BSVs should be of considerable relevance to the proper interpretation of clinical laboratory test results.
