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Saturday, September 20, 2014
Question about diabetes
I am a 38 year old woman, overweight, with a history of diabetes in the family. I often have to urinate frequently (sometimes several times a night)but do not have an infection. My doctor performed a Hemoglobin A1c test and the result was right at 6%. My fasting plasma glucose was 95mg after an 8 hour fast. Is it possible that I have diabetes even with negative results on these tests?
All tests that we use have strengths and limitations in making the diagnoses - we primarily characterize the sensitivity and specificity of a test result. Sensitivity is a measure of how likely the test is to pick up the diagnosis if the diagnosis is correct. Specificity is the likelihood that the diagnosis is correct if the test indicates the diagnosis is present. You would need to consider the sensitivity and specificity of these tests with your doctor. Alternative tests to consider include an oral glucose tolerance test which is probably more sensitive and specific than either of the tests mentioned for diabetes but performed less frequently because it requires more effort and modestly more cost. alternative diagnoses include diabetes insipidus for which a 24 hour urine volume would be helpful along with some other tests if your doctor thinks they are warranted.
Robert M Cohen, MD
Professor of Clinical Medicine
College of Medicine
University of Cincinnati