A recent analysis done on the Mexico City Diabetes Study indicates that many participants who were diagnosed as being either prediabetic or with type 2 diabetes were actually misdiagnosed. An oral glucose tolerance test showed that their glucose tolerance was within the normal range, while the HbA1c assay done during the study showed that they fell into the prediabetic or full diabetic range.
A team from the National Institute of Public Health in Mexico City noted that the HbA1c is known to have low sensitivity, something the ADA has stated before. This study confirmed such a low sensitivity, showing that as many as 45.5% of those in the study actually had normal oral glucose test results. Out of the 854 adults in the study, the oral test indicated that 30.5% had prediabetes, 9.4% had type 2 diabetes, and 59.9% were within normal range. The HbA1c, however, noted that 52.8% should be classified as having type 2 diabetes and another 32.9% should be classified as prediabetic.
Researchers did note that the findings were not necessarily representative of all Mexicans.
These findings were published in the Journal of the Endocrine Society on August 31, 2017.