Review Question - QID 211550

Figures 1 and 2 are the radiographs of a 41-year-old diabetic male presenting with right lower extremity pain after cutting his leg it on a piece of rusty metal yesterday. Serial physical exam demonstrates rapid progression of the overlying erythema and worsening pain. In the emergency department, labs are significant for a C-reactive protein (CRP) of 180 mg/L, white blood cell (WBC) count of 19,000/mm3, glucose of 11 mmol/L, creatinine of 150 umol/L, and sodium of 120 mmol/L. He has a temperature of 102°F and a heart rate of 110 bpm. What additional laboratory value is needed to calculate this patient’s LRINEC (Laboratory Risk Indicator for Necrotizing Fasciitis) score?