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Some of the Most Important Lab Tests and What They Mean

September/October 2011

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Serum Lipids

Diet, exercise, cigarette smoking, and your genetic heritage (the genes you inherited from your parents and ancestors) all influence your risk for heart disease. Since we now expect HIV-positive people to live a long time, we have to pay attention to the fact that both HIV itself and some of the medications used to treat it have been associated with abnormal lipid levels (cholesterol and triglycerides, which are fats in the blood). This makes it important to obtain fasting lipids when you first enter HIV care, and to have them repeated at least once a year. Repeating them more often will depend on whether they are normal or not to begin with and what other heart disease risks you have -- are you overweight? Do you smoke? Do you have diabetes or high blood pressure? Do you exercise? Do you have a family history of high cholesterol or heart disease?

To be accurate, lipid testing must be done in the "fasted" state -- no food (or drink, except water or diet soda or plain tea or black coffee -- any drink without calories) for a minimum of eight hours, ideally 10 to 12. Fasting lipids include four separate measurements of different forms of fats that circulate in your blood: total cholesterol, high-density lipoprotein (HDL, or "good cholesterol"), low-density lipoprotein (LDL, or "bad cholesterol"), and triglycerides.

High levels of HDL protect you against heart disease caused by clogged arteries in your heart (atherosclerotic heart disease). Unfortunately, high levels of the other fats are associated with an increased risk for heart disease. Lipid levels can be lowered with lifestyle changes, but some people may also have to take lipid-lowering drugs in addition to a diet change and other interventions.

Not that HIV-positive people have the prospect of living out a normal lifespan, it is important to provide cancer screening tests.

Pap Smear

A Pap smear involves scraping cells from the cervix or anus (usually with a tiny cotton swab), preparing them on a slide, and viewing them through a microscope. Every HIV-negative woman should be screened once a year for cell changes on the cervix that could lead to cervical cancer, but women who are HIV-positive should be screened twice in the first year of care, and then annually after that if their initial tests are negative.


Cervical cancer is caused by infection with certain strains of human papillomavirus (HPV). Cervical cancer is a real threat to HIV-positive women, especially at lower CD4 counts, and it became part of the case definition of AIDS in 1993. If caught early, it can be cured.

Anal Pap smears are still not standard of care due to limitations of the test and because an expert is needed to accurately analyze the results. The wealth of data that exists for cervical Pap smears does not exist for anal Paps, so questions remain about their reliability and predictability as a screening tool. In some centers, anal Paps have been an effective way to screen for anal carcinoma, but many centers lack health care providers and pathologists (the doctors who interpret Pap smears) who can perform this test reliably. There is also as yet no clearly-defined guidance about when the anal Pap shows abnormalities that have not yet become cancerous.

Although the anal Pap was developed initially for men who have sex with men who are thought to be susceptible to anal carcinoma because of sexually transmitted HPV infection, women can also benefit from such a test, even if they have not had anal sex, because of something called the "field effect." This refers to the fact that it is easier to spread HPV around the anogenital region than some other sexually transmitted infections.

Screening Tests for Cancer

Now that HIV-positive people have the prospect of living out a normal lifespan, it is important to provide cancer screening tests because most cancers are age-related.

Also, there is some evidence that people who are HIV-positive may be at higher risk for a broader range of cancers than the ones that have long been HIV-associated, like Kaposi's sarcoma and B cell lymphoma.

The guidelines for performing these screening tests are the same as those for HIV-negative individuals.

  • For men aged 40 and older: an annual prostate-specific antigen (PSA) blood test to look for prostate cancer is recommended, but controversial because this test is not very precise.
  • For women aged 40 and older: a baseline mammogram (type of x-ray) to detect breast cancer, with subsequent mammograms based on age and family history.
  • For all people aged 50 and older: a baseline colonoscopy to detect colon cancer that is repeated in 10 years, unless abnormalities are found or there is a strong family history of colon cancer.
  • For smokers: QUIT! A chest X-ray may be prudent for smokers with symptoms, but there is no clear interval for subsequent screening.

Additional Tests, When a Closer Inspection Is Warranted

Testosterone level. Among other key functions, testosterone is the hormone that drives sexual interest (libido) in both men and women, though normal levels for women are much lower than for men. Symptoms of low testosterone (hypogonadism) in men include: depression, lack of energy, reduced muscle mass, and decreased sex drive or arousal. Much less is known about women and testosterone, but low testosterone levels in women can also cause decreased sex drive.

Hypogonadism seems to be common in HIV-positive men, though it is not known why. Testosterone levels in men normally decline with age, so the level has to be interpreted with your age in mind.

Testosterone replacement can be done by injection every few weeks or by gels or patches that are applied to the skin every morning. It is difficult to replace testosterone in women because the amount needed is so small, and current doses of various testosterone preparations are geared for treating men.

Thyroid hormone level. Low levels of thyroid hormone (hypothyroidism) are fairly common in women, HIV-positive or not. Low thyroid levels can cause weight gain, lack of energy, depression, and skin changes. A thyroid stimulating hormone (TSH) level can screen for an underactive, as well as overactive, thyroid gland. Both underactive and overactive thyroid conditions can be treated.

DEXA (dual X-ray absorptometry) scan. This scan tells us about the composition of the various body compartments -- bone, fat, muscle -- and is particularly useful in determining whether you have lost a modest amount (osteopenia) or too much (osteoporosis) of your bone mineral content. Osteopenia and osteoporosis weaken your bones and make them prone to fractures or breaking.

Bone mineral loss can occur in men with low testosterone levels and women who have stopped having periods (menopause). It can also run in families. This problem can largely be avoided with a good intake of calcium (at least 500 mg per day in dairy foods and leafy greens or as a supplement) and vitamin D (from exposure to sunshine, in fortified milk, or as a daily supplement of 1,000 IU [international units]).

It is important to do the kind of exercise that makes your muscles tug on your bones, such as resistance exercises that use weights or elastic bands. Walking briskly several times a week is also helpful because you are bearing your own weight, which helps keep your bones strong. In addition to calcium, vitamin D, and exercise, you can treat severe bone mineral loss with a medication you take once a week or once a month to help reverse bone loss.

DEXA scans can also measure how much fat you have inside your body (visceral fat) and under your skin (subcutaneous fat), although this is more of a tool in studies of fat gain and loss (lipodystrophy) than a test used in the clinic to help with treatment of your HIV disease.

Judith Feinberg, M.D., is a clinician and Professor of Medicine at the University of Cincinnati, where she is also the Co-Director of the AIDS Clinical Trials Unit.

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This article was provided by Positively Aware. It is a part of the publication Positively Aware. Visit Positively Aware's website to find out more about the publication.
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