You can read an abstract of this study here:
Six of Eight Hemoglobin A1c Point-of-Care Instruments Do Not Meet the General Accepted Analytical Performance Criteria. Erna Lenters-Westra1, and Robbert J. Slingerland. Clinical Chemistry 56: 44-52, 2010. First published November 19, 2009; 10.1373/clinchem.2009.130641
The study concluded only two of the eight kits produced clinically valid results. What is most telling, though, is that the study reports: Because of disappointing EP-10 results, 2 of the 8 manufacturers decided not to continue the evaluation. Their test kits were removed from the study after they completed only one of three CLSI protocols that were planned. CLSI stands for "Clinical and Lab Standards Institute."
Since four of the six kits that remained in the study ended up with unacceptable results, but must have had good enough results after the first protocol to encourage their manufacturers to keep them in the study, one can only conclude that the kits removed from the study did abysmally.
Which meters were withdrawn from the study after they did very poorly at the first level of testing? A1c Now and Quo-test.
Of the six remaining kits that completed all three laboratory test protocols,
Only the Afinion and the DCA Vantage met the acceptance criteria of having a total CV <3% in the clinically relevant range.The CV is the "Coeeficient of variation." It is the statistic that represents the ratio of the standard deviation to the mean. It's a measure of how widely scattered data is. The larger it is, the more wide the range is that a set of data falls in. If a test kit produced a higher CV it tells you that using it repeatedly on the same sample produced an unacceptably broad range of results.
Even the kits that met the goals of the study had problems as the study concludes,
The EP-9 results and the calculations of the NGSP certification showed significant differences in analytical performance between different reagent lot numbers for all Hb A1c POC [point of care] instruments.In other words, there was significant variation from batch to batch.
What does this mean for you?
1. Don't waste your money on a home A1c test. The accuracy is abysmal. This is actually disclosed in the package but in a way that confuses people. The packages says the results will fall within .5% of the actual lab result, but people don't realize this means that a 6.5% reading from this test could mean you'd get a reading of 6.0% or one of 7.0% at the lab. This is a significant difference. I used the A1c Now home kit twice several years ago and it was off by .5% both times.
An article about this published in the newsletter for endocrinologists that tipped me off to this added that lab results nowadays are usually very accurate.
2. If your doctor wants to test your A1c in the office and tells you it will give you an immediate result, demand to know which kit was used and if it is not the Afinion or the DCA Vantage, refuse the office test. It will be highly inaccurate, though you will be charged for it as if it were a lab test. Opt for a lab test instead. If your doctor gets snarky, direct him to the Clinical Chemistry article and suggest he use a meter that will give accurate results.
This is important because doctors often use nothing but the A1c to diagnose and gauge the progress of their patients. With the large variations from the true value you may get with an inaccurate test kit, you may think you are doing well when you are not, or vice versa.
3. If you are diagnosed with diabetes for the first time after being given an in office A1c test, be aware that this test is being administered for convenience. It is not a particularly accurate way of measuring your blood sugar. Get a blood sugar meter and test your blood sugar both first thing in the morning and one hour after each meal. If you see numbers over 200 mg/dl (11 mmol/L) at any time, you can be confident you are in fact diabetic. If you see only numbers between 140 mg/dl (7.7 mmol/L) and 199 mg/dl (11 mmol/L) after eating, you technically have "pre-diabetes", but your post-meal numbers are high enough to damage your heart, retinas, and nerves as this is the range where solid research demonstrates that "diabetic" complications begin to occur.
You can learn more here about Research Connecting Blood Sugar Levels With Complications.
You can learn how to lower your blood sugar levels to the safe range here: How To Get Your Blood Sugar Under Control
One final thought. You probably don't want to know what careful testing would find out about the CV of the obscenely expensive blood sugar test strips we rely on. The fact that we patients put up with $1.20 a piece strips that can vary by as much as 40 mg/dl(plus or minus) from the true reading at a reading in the mid 200s and by 20 mg/dl plus or minus at normal ranges is criminal.