A 50-year-old male patient presented to the dermatology OPD with characteristic skin lesions on the right shin. The skin lesion is a single indurated yellowish-brown plaque with atrophic centre. Some ectatic blood vessels are visible through the thinned skin. A biopsy sample was taken and HPE examination was done. Which of the following is the next best investigation to be done in the patient: -

This is a case of necrobiosis lipoidica diabeticorum. It is seen in patients of Diabetes mellitus. So, it is advised to go for testing of blood sugar levels to rule out diabetes. HPE examination shows: - Several layers of necrobiosis Superficial and deep perivascular infiltrate Interstitial mixed inflammatory cell infiltrate in dermis Septal panniculitis Lymphoid cell aggregates in deep dermis and subcutis