Laboratory Tests for Wound Care
The essential laboratory tests for wound care include wound cultures (tissue specimens preferred over swabs), blood cultures for severe infections, serum lactate or base deficit for shock assessment, and glucose monitoring in diabetic patients, with additional tests guided by infection severity and patient comorbidities.
Microbiological Testing
Wound Cultures
Obtain tissue specimens from the debrided wound base via curettage or biopsy rather than swabs, as tissue samples from the advancing margin represent the true disease process while surface swabs are inadequate 1, 2.
Cleanse and debride the wound thoroughly before specimen collection, removing all topical antimicrobials that could affect culture results 1, 2.
Cultures are valuable for directing antibiotic therapy in moderate-to-severe infections but may be unnecessary for acute mild infections in antibiotic-naive patients 1.
Do not culture clinically uninfected wounds unless part of infection-control surveillance 1.
Request both aerobic and anaerobic cultures, particularly for deep tissue infections and bite wounds 2.
Clearly label specimens with anatomic location and wound type, and transport rapidly to the laboratory in appropriate sterile containers 1.
Blood Cultures
- Obtain blood cultures for patients with severe infections, especially if systemically ill (fever, leukocytosis, metabolic instability) 1.
Metabolic and Perfusion Assessment
Glucose Monitoring
Monitor blood glucose levels closely in diabetic patients, as hyperglycemia (>200 mg/dL) significantly increases wound infection risk and impairs healing 3.
Maintain mean blood glucose <200 mg/dL in the postoperative period to reduce deep wound infection rates 3.
Shock and Tissue Perfusion Markers
Measure serum lactate or base deficit to estimate and monitor the extent of bleeding and shock in trauma-related wounds 1.
These markers provide more reliable assessment of tissue perfusion than single hematocrit measurements 1.
Coagulation Studies
Obtain early and repeated measurements of PT, APTT, fibrinogen, and platelet counts to detect post-traumatic coagulopathy in bleeding wounds 1.
Consider viscoelastic testing to characterize coagulopathy and guide hemostatic therapy 1.
Vascular Assessment Laboratory Tests
Measure ankle-brachial index (ABI) using Doppler in all diabetic foot ulcer patients, as peripheral arterial disease is present in 20-40% of cases 1, 4.
An ABI <0.6 indicates significant ischemia affecting wound healing potential 1.
Measure toe-brachial index or transcutaneous oxygen pressure (TcPO2) when ABI is unreliable due to arterial calcification (common in diabetes) 1, 4.
Toe pressure >55 mmHg and TcPO2 >50 mmHg predict adequate healing potential, while values <30 mmHg severely impair healing 1.
Additional Considerations
Nutritional Assessment
- Consider albumin, prealbumin, and micronutrient levels in patients with chronic wounds, as suboptimal nutrition alters immune function, collagen synthesis, and wound tensile strength 5.
Timing of Cultures
Do not submit specimens for culture within the first 48 hours post-trauma, as growth likely represents environmental contamination rather than true infection 2.
The optimal time for culture acquisition is immediately post-debridement 2.
Critical Pitfalls to Avoid
Never rely solely on swab cultures, as they may not accurately represent the true pathogenic organisms causing infection 2.
Avoid requesting the laboratory to "report everything that grows," which leads to treatment of colonizing organisms rather than true pathogens 2.
Do not use single hematocrit measurements as an isolated marker for bleeding in trauma wounds 1.
Do not attribute poor healing solely to "diabetic microangiopathy"—always assess for correctable vascular insufficiency 4.