HbA1c of 6.5% to Diagnose Diabetes Mellitus — Does It Work for Us? — The Bellville South Africa Study

Abstract

BackgroundHbA1c has been the gold standard for glycaemic control follow-up for decades. In 2009, a level of 6.5% (48 mmol/mol) was proposed as diagnostic for diabetes. We test this cut-off in our community.MethodsParticipants (946) from a community-based study were screened for diabetes using either a fasting blood glucose or oral glucose tolerance test (OFTT). The HbA1c cut-off of 6.5% was tested for each group. A receiver operator characteristic (ROC) curve for both groups was generated to establish an optimal cut-off.ResultsOur study included 224 (23.7%) males and 722 (76.3%) females. Using fasting blood glucose alone, 117 (14%) were diagnosed with diabetes −50% had an HbA1c value of ≥6.5% (48 mmol/mol). Using an OGTT, 147 (18%) were diagnosed with diabetes −46% had an HbA1c value of ≥6.5% (48 mmol/mol). ROC curves found a level of 6.1% (43 mmol/mol) to be optimal in both groups (AUC 0.85 and 0.82 respectively). The sensitivities were 80% and 75% and the specificities 77% and 78% respectively.ConclusionsA cut off of 6.5% (48 mmol/mol) is a good diagnostic tool with its high specificity; however the low sensitivity limits its use. We found a level of 6.1% (43 mmol/mol) to be optimal. This emphasizes the need for evidenced based values to be established in various population groups.

Contribution of ENPP1, TCF7L2, and FTO polymorphisms to type 2 diabetes in mixed ancestry ethnic population of South Africa

“…The population group has lived in Bellville South since late 1950s. A detailed description of the survey and procedures conducted in the study are available elsewhere 26,27 .…”

Glycemic control in the clinical management of diabetic patients

“…In a Chinese population (2332 subjects aged 35 -74 years), using the diagnostic cut-off of 6.5% (48 mmol/mol) for HbA 1c generated a sensitivity of < 30% in both men and women, i.e., lower than for plasma glucose. The optimal cut-off for detecting diabetes in this population was an HbA 1c level of 5.6% (38 mmol/ mol), i.e., significantly lower than in the new ADA recommendations [ 49 ], but this cut-off proved unsuitable for the South African population, for which Zemlin et al identified a level of 6.1% (43 mmol/mol) as the optimal cut-off [ 54 ].…”

A study on assessment of HbA1c level as a diagnostic criterion of type 2 diabetes mellitus

“…The cut-off value of HbA1c for diagnosis of diabetes has been a matter of controversy and debate worldwide. Gomyo et al, 9 Farhan et al, 10 Adamska et al, 11 Martin et al, 12 Bae et al, 13 Zemlin et al, 14 Tankova et al, 15 Ghazanfari et al, 16 Li et al, 17 Kim et al 18 had proposed values of 5. 23,24 (ABCD) gives an even higher level of 7.2% to rule in diabetes.…”