Initial Lab Workup for Nonhealing Foot Wound
For any nonhealing foot wound, obtain blood tests for glycemic control (hemoglobin A1c), inflammatory markers (C-reactive protein, erythrocyte sedimentation rate), complete blood count with differential, basic metabolic panel, and assess nutritional status with albumin, total protein, hemoglobin, iron, and zinc levels. 1, 2
Essential Laboratory Tests
Metabolic and Glycemic Assessment
- Hemoglobin A1c to evaluate glycemic control, as hyperglycemia directly impairs wound healing and increases infection risk 1, 3
- Basic metabolic panel to identify electrolyte abnormalities, new or worsening azotemia, and acidosis that may indicate severe infection or metabolic instability 1
- Random or fasting glucose to assess current glycemic status 1
Inflammatory Markers and Infection Assessment
- C-reactive protein (CRP) - levels >2 standard deviations above the upper limit of normal suggest serious infection 1
- Erythrocyte sedimentation rate (ESR) - markedly elevated levels indicate possible deep infection or osteomyelitis 1
- Procalcitonin - levels >2 standard deviations above normal suggest severe infection 1
- Complete blood count with differential - leukocytosis indicates infection, though 50% of patients with limb-threatening infections lack systemic signs 1
Nutritional Status Assessment
- Serum albumin - low in 37% of diabetic foot patients and critical for wound healing 2
- Total protein - frequently deficient in diabetic foot patients 2
- Hemoglobin - low in 89% of diabetic foot patients, with lower levels correlating with older age and longer hospital stays 2
- Iron levels - deficient in 97% of diabetic foot patients 2
- Zinc levels - low in 95% of diabetic foot patients and essential for wound healing 2
Additional Metabolic Parameters
- Lactate - hyperlactataemia (>1 mmol/L) suggests serious infection 1
- HDL and LDL cholesterol - part of cardiovascular risk assessment, as HDL is often low in diabetic foot patients 3, 2
Blood Cultures
- Obtain blood cultures for any patient with severe infection or systemic illness (fever, chills, hypotension, confusion) 1
- Blood cultures are particularly important when systemic toxicity is present, even if local signs are minimal 1
Critical Considerations
When Labs Suggest Serious Infection
The combination of severely elevated inflammatory markers, leukocytosis, severe hyperglycemia, acidosis, and electrolyte abnormalities indicates a potentially life-threatening infection requiring immediate hospitalization and aggressive management 1
Nutritional Deficiencies
The evidence strongly suggests that albumin, hemoglobin, iron, and zinc deficiencies are nearly universal in diabetic foot patients and likely impair wound healing - these should be identified and corrected 2. While the 2016 IWGDF and 2004 IDSA guidelines focus primarily on infection markers 1, the 2024 research demonstrates that nutritional parameters are critically low in most patients and warrant routine assessment 2.
Common Pitfalls to Avoid
- Do not rely solely on inflammatory markers or white blood cell count to rule out infection, as peripheral neuropathy can mask systemic signs in up to 50% of severe infections 1
- Do not overlook nutritional deficiencies - these are present in the vast majority of diabetic foot patients and directly impact healing capacity 2
- Do not delay obtaining cultures if infection is suspected, as empirical antibiotic therapy should be guided by culture results when possible 1
Integration with Clinical Assessment
These laboratory tests should be obtained at initial evaluation alongside vital signs, wound debridement, probing to assess depth, and vascular assessment 1. The lab results help determine infection severity, guide antibiotic selection, identify metabolic instability requiring hospitalization, and reveal nutritional deficiencies that must be corrected for optimal healing 1, 2.