I am deeply interested in the subject of glycemia/HbA1c relationships, underlying mechanisms, and impact on the assessment of glycemic control and diabetes prevalence. In the article by Soranzo et al. (1) published in Diabetes, the abstract indicates that adjusted HbA1c would imply the reclassification of about 2% of the subjects in a general Caucasian population.

The table provided in Fig. 3 of that article is displayed below (Table 1) with the blank spaces filled with the corresponding figures and my reading of it.

• Undiagnosed diabetes according to fasting plasma glucose 593/10,110 = 5.87%.

• Undiagnosed diabetes according to measured HbA1c ≥6.5% = (234 + 112)/10,110 = 346/10,110 = 3.42%.

• Undiagnosed diabetes according to 7 single nucleotide polymorphism (SNP)-adjusted HbA1c ≥6.5% = (222 + 96)/10,110 = 318/10,110 = 3.15%.

TABLE 1

Reclassification of diabetes diagnoses performed using HbA1c when genetic information is taken into account

 7 SNP-adjusted <6.5%* >6.5%* Total Undiagnosed diabetes <6.5%* 358 1 359 >6.5%* 13 221 234 Subtotal 371 222 593 Nondiabetes <6.5%* 9,404 1 9,405 >6.5%* 17 95 112 Subtotal 9,421 96 9,517 Total 9,792 318 10,110
 7 SNP-adjusted <6.5%* >6.5%* Total Undiagnosed diabetes <6.5%* 358 1 359 >6.5%* 13 221 234 Subtotal 371 222 593 Nondiabetes <6.5%* 9,404 1 9,405 >6.5%* 17 95 112 Subtotal 9,421 96 9,517 Total 9,792 318 10,110

Data are n.

*

HbA1c.

At the population level, should diabetes diagnosis be performed using HbA1c, adjustment for 7 single nucleotide polymorphisms, would imply a net reclassification of 28 out of 10,110 subjects, an absolute difference in new diagnosis of −0.27% (3.15–3.42%) and a relative reduction of −7.9% (−0.27/3.42) × 100.

1.
Soranzo
N
,
Sanna
S
,
Wheeler
E
, et al
.
Common variants at 10 genomic loci influence hemoglobin A1C levels via glycemic and nonglycemic pathways
.
Diabetes
2010
;
59
:
3229
3239