Variability of the lateral position test in normal subjects

An evaluation of the variability of the lateral position test (LPT) in normal subjects was undertaken. In 10 healthy, nonsmoking young adults, tests were performed in triplicate for 5 consecutive days. The results indicate that sizable differences in determinations of unilateral pulmonary function by the LPT can exist from day to day and from test to test on any given day in any given person. Variability of repeated measurements by the same observer and of measurements by different observers was minimal. In view of the great variability in repeated LPT results on the same subject, it is necessary to perform several tests in each subject before meaningful interpretation of the data can be made. This limits the usefulness of the LPT in the clinical assessment of unilateral pulmonary function.