Problems of interpretation of laboratory findings in the old.

Haematological, biochemical, and endocrine disorders are common in old age, and are often eminently remediable, but assessment of their significance is frequently hampered by problems of interpretation of the laboratory data on which the diagnosis and management of such disorders usually rest. There are several reasons for these difficulties in interpretation. Simpie lack of knowledge of well-established normal values is not infrequent. Many normal values in the elderly are identical to those recognized for the young. If an abnormal value is mistakenly considered to be normal "for the patient's age," the opportunity for correct diagnosis and active treatment will be missed. Conversely some normal values differ in the elderly from those taught for the young. If a value normal for the patient's age is considered abnormal, then the patient may be subjected to unnecessary and possibly even hazardous further investigations-or an incorrect diagnosis and so perhaps prognosis will result. In both instances the necessary information may be found in journals which are not easily accessible, may not yet be in the textbooks, and in consequence is not taught. A further difficulty arises from the fact that some normal values are not yet certainly established for the elderly. One reason for this is the high frequency of disease states in old age, which may make distinction of normal from abnormal uncertain. There is often in addition a problem in assessing the significance of minor deviations from normality as shown by laboratory tests in old people, and consequent difficulty in management of patients with such abnormalities. The present paper attempts to review and discuss in respect of the elderly several commonly performed laboratory tests and the problems of interpretation which they present, both in relation to screening procedures and to the assessment of sick old people.