For example, isoniazid, levodopa, morphine, vitamin C, nalidixic acid, and penicillin G may lead to false-positive urine glucose results. Levodopa may produce a spurious increase in serum bilirubin and uric acid, also leading to false-positive results. A low serum albumin level in healthy elderly persons is usually due to diet. However, low levels may also indicate serious disease, especially when accompanied by undernutrition. Fasting blood glucose levels increase with age, although values remain within the nondiabetic range.
Glucose tolerance decreases gradually with age.
However, lack of exercise, obesity, and the use of some drugs may affect glucose tolerance more than aging per se. The renal threshold for glucose decreases with age. If elderly patients have an unexplained elevation in the ESR, a monoclonal gammopathy should be sought. Consequently, its value in screening for prostate cancer is debatable. For men with an abnormal prostate detected by rectal examination, PSA may be measured, but this measurement may be less valuable than the ratio of PSA to gland size, and abnormal results are likely to lead to more expensive, invasive tests.