17-hydroxyprogesterone is elevated in patients with congenital adrenal hyperplasia (CAH). CAH is a group of autosomal recessive diseases characterized by a deficiency of cortisol and an excess of ACTH concentration. 17-hydroxyprogesterone is also useful in monitoring cortisol replacement therapy and in evaluating infertility and adrenal and ovarian neoplasms.
Increased CRP levels are found in inflammatory conditions including: bacterial infection, rheumatic fever, active arthritis, myocardial infarction, malignancies and in the post-operative state. This test cannot detect the relatively small elevations of CRP that are associated with increased cardiovascular risk.
A large percentage of patients with gastrointestinal tumors (such as pancreatic, liver, gastric, colorectal tumors) and some other malignancies have been shown to have elevated serum CA 19-9 levels. Serum CA 19-9 levels may be useful for monitoring disease activity or predicting relapse following treatment. CA 19-9 should not be used as a screening test.
Serum calcium is involved in the regulation of neuromuscular and enzyme activity, bone metabolism and blood coagulation. Calcium blood levels are controlled by a complex interaction of parathyroid hormone, vitamin D, calcitonin and adrenal cortical steroids. Calcium measurements are useful in the diagnosis of parathyroid disease, some bone disorders and chronic renal disease. A low level of calcium may result in tetany.
Specimens from children less than 4 years of age (i.e., less than 48 months) are not appropriate for this test. The test for children 4 years of age and younger is the Celiac Disease Comprehensive Panel, Infant (test code 15981).
Serum creatinine is useful in the evaluation of kidney function and in monitoring renal dialysis. A serum creatinine result within the reference range does not rule out renal function impairment: serum creatinine is not sensitive to early renal damage since it varies with age, gender and ethnic background. The impact of these variables can be reduced by an estimation of the glomerular filtration rate using an equation that includes serum creatinine, age and gender.
Vitamin A is critical for vision, growth, and many cell functions. High concentrations of vitamin A are seen with renal failure, but this is not associated with toxicity, and excessive ingestion.