February 12, 2002
A1c (Glycohemoglobin, HgbA1c)
Question from Onsted, Michigan, USA:
What is the typical standard deviation for the A1c test?
Answer:
If you are using standard deviation as a measure of the reliability of a hemoglobin A1c test, the best figures are those from the American College of Pathology EXCEL proficiency testing program. In a recent report on 109 laboratories all using the DCA 2000 program, the standard deviation on a sample mean of 5.93% was 0.3 which gives a variance (S.D./mean x 100) of 5% and 95% confidence limits of about twice this. The second most commonly used method however had a variance of more than 10%, and at the other end of the scale, in an individual laboratory where a single person does all the tests and maintains the instruments the variance may be less than 3.0%.
DOB
[Editor’s comment: See also HbA1c Measurement and The National Glycohemoglobin Standardization Program.
JSH]
