A1c Predicts Diabetic Wound Healing

Worse glycemic control correlated with slower wound healing in patients with diabetes. Every 1% increase in HbA1c was associated with -0.028 cm2decrement in the daily change in wound area....

Every 1% increase in hemoglobin A1c was associated with almost a 0.03 cm2reduction in daily rate of wound resolution. Diabetic patients with peripheral neuropathy or peripheral arterial disease (PAD) were especially susceptible to the impact of glycemic control on wound healing.

In a multivariate analysis, hemoglobin A1c, used as a surrogate for glycemic control, was the only independent predictor of change in wound area, according to a report.

Anna L. Christman, BA, of Johns Hopkins University in Baltimore, stated that, "Our results suggest that better glycemic control could help wound healing in diabetic patients, but that would have to be confirmed in a prospective clinical study."

"It would seem logical that glycemic control would affect wound healing, but to our knowledge, this is the first time the association has been clearly demonstrated," she added.

"Previous studies had evaluated the effect of glucose levels on the risk of amputation, and the results were inconsistent. Ours is the first study to use digital imaging of wounds to examine the association."

Diabetes continues to be a major contributor to lower-leg amputations, ranking second only to trauma as a cause. The necessity of amputation in diabetic patients arises from disease-related neuropathy and vasculopathy.

Identification of modifiable factors that influence wound healing could help reduce the need for amputation, Christman and colleagues noted in a poster presentation. To that end, they performed a retrospective cohort study to identify clinical variables associated with wound healing.

Investigators hypothesized that elevated A1c levels would be the strongest predictor of poor wound healing among common laboratory and clinical measures.

The study involved 183 diabetic patients with an average of 310 wounds and a total wound area that averaged 7.2 cm2. Clinical evaluation of the patients included blood pressure, pulse, temperature, and assessment of peripheral neuropathy status. Laboratory values of interest included HbA1c, total cholesterol, LDL, HDL, triglycerides, and white blood-cell count, as well as body mass index (BMI), smoking status, and presence of PAD.

The primary outcome was the change in the size of the wound area as determined by calibrated tracings of digital images. The impact of clinical variables on wound healing was assessed by multiple linear regression and investigators stratified the results by peripheral neuropathy status and PAD status.

The patients had a mean age of 61, with men and whites each accounting for 55% of the study population. The BMI averaged 35. The mean HbA1c was 8.0%, including 71 patients with values more than 7%, 42 patients with levels of 7.0 to 8.0%, and 70 with HbA1c values >8%.

A majority of the study group (60%) had peripheral neuropathy and 29% had PAD. The patients had an average of 2.3 wounds with a total wound area of 7.2 cm2.

In the overall analysis, HbA1c remained the only significant predictor of the change in wound area per day. Every 1% increase in HbA1c was associated with -0.028 cm2 decrement in the daily change in wound area (P=0.03).

The association remained significant in the stratified analyses. Among patients with peripheral neuropathy, each 1.0% increase in HbA1c was associated with a 0.022 cm2 decrease in the daily wound-healing rate (P=0.043).

Patients with PAD had a decrease in healing rate of 0.030 cm2 for every 1% increase in HbA1c (P=0.046).

Practice Pearls
Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
Explain that a retrospective cohort study found diabetics with higher HbA1c had a significantly slower rate of wound healing than those with lower HbA1c.
Note that wound healing rates were calculated from calibrated tracings of digital wound images
Christman AL, et al "Hemoglobin A1ac predicts healing rate in diabetic wounds" SID 2011; Abstract 204