Quest Diagnostics admitted in early January that thousands of its vitamin D tests conducted over the last two years were incorrect. In a letter to doctors, Quest said the test has now been fixed and offered free retests. Vitamin D deficiency has been linked to several diseases, and test volumes have doubled on an annual basis, according to some providers. However, the test is not standardized and there is debate about treatment options. Quest explained that the problem arose when it switched in 2007 from a FDA-regulated test to a test that it had developed. Tests developed by single labs do not require FDA approval. The new test uses MS. Quest stated that calibration materials were at fault and that four of its seven labs did not follow proper testing procedures. The incorrect results accounted for less than 10% of all vitamin D tests done by the company between early 2007 and the middle of 2008. Quest discovered the problem when it reviewed national data.

Source: New York Times