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Serum cholesterol testing in adults is recommended every 1 to 5 years. People with diabetes and a family history of high cholesterol should be tested even more frequently.
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.
When Gabriel Fahrenheit invented the first mercury thermometer, he called "zero degrees" the lowest temperature he was able to attain with a mixture of ice and salt. For the upper point of his scale, he used 96°, which he measured as normal human body temperature (we know it to be 98.6° today because of more accurate thermometers).
The U.S. Preventive Services Task Force recommends that all women age 65 years of age or older should be screened with bone densitometry.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
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