Not ready for prime-time as screening tool

QUESTION: I’m a healthy woman. I recently had a whole-body thermography exam that highlighted my thyroid rather dramatically. Should I get a blood test for my thyroid and/or an ultrasound?

ANSWER: Thermography is a technique looking at differences in skin temperature. Back in the 1970s, it was found that breast cancer can lead to warmer temperatures on the skin overlying the tumor. Unfortunately, there still has not been any evidence that thermography has any advantages over mammography. Recent research suggests there may be a role in the future for thermography, possibly in combination with mammography, but the data on breast cancer shows poor accuracy.

An overactive thyroid gland may also lead to high blood flow and warmer skin temperatures. So theoretically, thermography could be used to diagnose thyroid tumors and hyperthyroidism. Again, there may be potential in the future but in my opinion, thermography is not an appropriate screening test in a healthy person.

Although I recommend against getting a screening thermography exam, now that you have documented an abnormality, your doctor may feel obligated to do an evaluation. Since the whole thyroid was abnormal by thermography, rather than a specific area, as it would be in the case of a tumor, a set of thyroid function blood testing may help relieve the anxiety you must feel with this abnormal test.

Screening tests need to be proven both safe and effective. False positive tests lead to anxiety and unnecessary followup testing. False negative tests can keep a person from coming to the doctor to get evaluated. Screening tests require a very high level of evidence before they can be recommended, and thermography is not yet ready for use in screening.

QUESTION: Can you explain diabetes and gangrene? I am prediabetic and the second toes on both feet have some tiny black spots on them. I will see my primary care physician soon.

— S.R.

ANSWER: Gangrene is a name for localized death of body tissues. There are several different types. Gas gangrene is a rapid, life-threatening infection caused by virulent micro-organisms, such as group A streptococci or Clostridium perfringens. Gas gangrene is fortunately uncommon to see these days, as it is often a complication of delayed treatment of wounds.

It is called gas gangrene because the bacteria make gas, which can be felt under the skin. This is usually very painful. Treatment is rapid and extensive surgery along with antibiotics, and hyperbaric oxygen is a sometimes-useful additional treatment. This is the type of gangrene least associated with diabetes.

Dry gangrene is caused by poor blood flow, usually to an extremity. People with longstanding, severe diabetes are more at risk for this due to damage to both small and large blood vessels. The skin appears dark and dry. Treatment usually includes surgery to improve the blood supply if possible; without it, the damaged tissues won’t heal.

Wet gangrene is a life-threatening emergency requiring immediate surgery. People with diabetes and nerve damage (neuropathy) are at higher risk for this, because they can injure themselves without knowing it. The tissue appears wet, swollen and blistered, and may have a bad odor.

While dark spots on the toes could possibly be gangrene, it would be very unlikely in a person with prediabetes. Your primary care physician or diabetes educator should be instructing you on what to look for on your feet (you should do a quick check every day) and to come in promptly for any worrisome signs. People with diabetes may also benefit from regular foot care from a podiatrist, who can help prevent foot problems from developing.