American Medical Association Family Medical Guide - American Medical Association [113]
Uric acid
Uric acid is a by-product of metabolism that normally is excreted by the kidneys in urine. An increase in the amount of uric acid can be a sign of gout, kidney failure, or lead poisoning. Drugs such as alcohol, diuretics, and caffeine can increase the amount of uric acid in the blood. The normal uric acid range is 2.6 to 7.8 milligrams per deciliter (mg/dL).
Blood Culture
In a blood culture, blood is drawn from a vein on the inside of an elbow or from the back of the hand and examined over several days. A blood culture is used to check for the growth of bacteria and other microorganisms in the blood. The presence of bacteria in the blood indicates a life-threatening infection called bacteremia.
PSA Test
The PSA (prostate-specific antigen) test measures the level in the blood of a protein called PSA, which is produced by cells in the prostate gland. The level can be increased when a man has prostate cancer or a noncancerous condition such as inflammation of the prostate or enlargement of the prostate. The test is often used along with a digital rectal examination to screen for and diagnose prostate cancer in men age 50 or older. Because blacks are at higher risk than whites of developing prostate cancer, black men (and all men who have a family history of prostate cancer) should start having the PSA test at about age 45. The test is also used, with other tests, to detect a recurrence of prostate cancer in men who have undergone treatment for prostate cancer.
A PSA level of fewer than 4 nanograms per milliliter (ng/mL) is considered normal. If your PSA level is elevated, your doctor will recommend further testing, including imaging tests or a biopsy (taking a small tissue sample from the prostate for examination under a microscope). Most men who have an elevated PSA level, especially those over age 50, are found not to have prostate cancer on further testing. Talk to your doctor about the pros and cons of having an annual PSA test and possible follow-up procedures if the level is elevated.
CA-125 Test
In the CA-125 test, a sample of a woman’s blood is examined for the presence of a chemical marker (antigen) called CA-125 on the surface of cells to help diagnose ovarian cancer. Most women who have ovarian cancer have an elevated level of CA-125 in their blood. However, this test is not used as a screening test for ovarian cancer or to make a definite diagnosis of ovarian cancer because levels of CA-125 also can be elevated in noncancerous conditions such as inflammation in the abdomen, pelvic infections, uterine fibroids, ovarian cysts, endometriosis, and liver diseases such as hepatitis and cirrhosis. The CA-125 test is often used, usually along with other tests, to monitor the effectiveness of treatment of ovarian cancer in women who are undergoing chemotherapy.
A CA-125 level below 35 units per milliliter (U/mL) is considered normal. If your level of CA-125 is higher than normal, your doctor will recommend further tests, such as a vaginal ultrasound (see page 510), to make a diagnosis.
Thyroid Hormones
The thyroid gland produces two thyroid hormones, called thyroxine (T4) and triiodothyronine (T3), which can be measured in the blood to help doctors evaluate thyroid function. The thyroid’s hormone production is triggered by secretion of a hormone called thyroid-stimulating hormone (TSH) by the pituitary gland in the brain. Doctors usually use a combination of two or more tests to diagnose thyroid disorders. For example, a high level of TSH and a low level of T4 can indicate an underactive thyroid gland (hypothyroidism). An abnormally low level of TSH and high level of T4 can indicate an overactive thyroid gland (hyperthyroidism). The normal range for total T4 is 4.6 to 12 micrograms