Interprétation des examens de laboratoire chez la personne âgée : effet de l'âge ou du vieillissement

The clinical pertinence of laboratory tests is conditioned by the use of well-documented databases on biological variability. Knowledge of these variations in the pediatric and adolescent population is well established. On the other hand, the situation is not so obvious for the elderly population. This population is generally not homogeneous and well-defined physiological variations are scarce. The observed variations generally reflect infraclinical or chronic illnesses. Interindividual variation is generally higher in the elderly population than in younger subjects. Thus, it would be more judicious to classify older persons as a function of their functional performance. This raises the issue of the proper definition of “good health” during the aging process. The criteria usually used for young adults should be revisited. The relationship with age is in fact variable from one assay to another: sometimes low, non significant or on contrary extremely wide. Well-adapted reference intervals are a prerequisite to proper interpretation of laboratory data in the elderly population. In some instances however, reference limits may be unsuitable, e.g. when the biological variability is too large, reference limits used for younger adults should be applied, while in other cases, traditional reference limits must be applied for decision-making limits.