Complete Blood Count (CBC)

A complete blood count, or CBC, is a common blood test that measures the different cells in your blood, including red blood cells, white blood cells, and platelets. It gives your doctor a broad picture of your overall health and can help detect a wide range of conditions.

The 17-Hydroxyprogesterone (17-OHP) test measures the amount of 17-hydroxyprogesterone in your blood. This is a hormone produced by the adrenal glands, which sit on top of your kidneys. The 5th specimen post challenge means this is the fifth blood sample collected after you or your child received a hormone stimulation test (ACTH stimulation test) to check how the adrenal glands are working.

Your doctor may order this test as part of a routine checkup, to look into symptoms such as fatigue, weakness, fever, or unusual bruising, or to monitor an existing condition like anemia, infection, or a bleeding disorder. It is also used to see how treatments, such as chemotherapy, are affecting your blood cells.

This test is primarily used to diagnose and monitor congenital adrenal hyperplasia (CAH), a genetic disorder that affects the adrenal glands' ability to produce cortisol and sometimes aldosterone. CAH can cause abnormal hormone levels that lead to various symptoms, including early puberty, irregular periods, infertility, and in severe cases, salt-wasting crises in newborns. The ACTH stimulation test helps distinguish between different types of adrenal disorders.

The test is done by drawing a small sample of blood from a vein, usually in your arm. A healthcare provider will clean the site, insert a thin needle, and collect the blood into a tube. The procedure takes only a few minutes, and you may feel a brief sting. A small bandage is placed on the spot afterward.

A healthcare professional will first give you or your child an injection of ACTH (adrenocorticotropic hormone) to stimulate the adrenal glands. Blood samples are then collected at specific time intervals (this is the 5th specimen). The procedure is similar to a regular blood test - a needle will be inserted into a vein in your arm to collect the blood sample.

Your results show whether your blood cell counts fall within normal ranges. High or low values can point to conditions such as anemia, infection, inflammation, or clotting problems. Abnormal results do not always mean a serious illness, so your doctor will interpret them together with your symptoms, medical history, and other tests.

Normal results vary by age. Elevated 17-OHP levels after the ACTH stimulation test typically indicate congenital adrenal hyperplasia. Your healthcare provider will interpret the results based on the specific values, your symptoms, and other test results. Further genetic testing may be recommended to confirm the diagnosis and determine the specific type of CAH.