Laboratory Values in Chronic Wound Management
Wound healing is a complex process that uses specific cellular and biochemical actions to achieve wound closure. These processes—homeostasis, inflammation, proliferation, and maturation—occur over defined periods of time. They are often taken for granted as the wound innately granulates, contracts, and epithelializes under optimal conditions.
A wound begs the clinician’s attention when the healing processes stall and the wound doesn’t progress to closure. This type of wound is deemed chronic; it’s defined as an insult or injury that has failed to proceed through an orderly and timely process to produce anatomic and functional integrity, or that has proceeded through the repair process without establishing a sustained anatomic and functional result.
Despite advances in wound care over the last few decades, many chronic wounds continue to be affected by local and systemic factors that impair the healing process. Local factors include bacterial load and infection, trauma, edema, pressure, and moisture. Systemic factors include age; chronic medical conditions, such as anemia, diabetes mellitus, and renal or hepatic dysfunction; stress; medications; tissue oxygenation; and nutritional status, such as vitamin, protein, or fluid deficiencies.
Clinicians commonly evaluate and manage the typical chronic wounds, such as pressure ulcers, vascular ulcers, and diabetic ulcers. However, many unusual wounds mimic these common chronic wounds. Because these unusual wounds are often incorrectly assessed, they’re also misdiagnosed. Examples of conditions featuring unusual wounds include pyoderma gangrenosum, calciphylaxis, toxic epidermal necrolysis, epidermolysis bullosa, polyarteritis nodosa, antiphospholipid antibody syndrome, cryoglobulinemia, cholesterol emboli, disseminated intravascular coagulation/purpura fulminans, bullous pemphigoid, and necrotizing fasciitis.
MISDIAGNOSIS
Misdiagnosis of a wound prolongs the patient’s suffering by delaying healing; increasing the emotional and financial toll on the patient, caregiver, and facility; and increasing medical liability. It also leads to improper medication delivery and improper topical treatments, which further exacerbates the patient’s condition, covers up symptoms, prolongs the wrong diagnosis, and increases the patient’s morbidity or mortality.
This point is well illustrated in an article by Weening and associates on skin ulcers misdiagnosed as pyoderma gangrenosum. The authors reviewed 8 years’ worth of charts (240 from their facility and 157 from another one) in which wounds were diagnosed as pyoderma gangrenosum, but 10% of these were found
to be misdiagnosed for a median of 10 months. The authors concluded that misdiagnosis exposes patients to substantial risks associated with the wound’s treatment, and a thorough workup is needed to rule out diagnoses that mimic pyoderma gangrenosum.
to be misdiagnosed for a median of 10 months. The authors concluded that misdiagnosis exposes patients to substantial risks associated with the wound’s treatment, and a thorough workup is needed to rule out diagnoses that mimic pyoderma gangrenosum.
Tools to avoid misdiagnosis
Clinicians can reduce the chance of misdiagnosing a wound by using the following tools:
the medical record, to accurately describe the wound’s characteristics at each patient visit
risk assessment tools, which ensure systematic evaluation of individual risk factors
nutritional risk assessment tools
manual screening tools, including the ankle-brachial index, lower leg and foot assessments, palpation of pulses and Doppler ultrasound, segmental blood pressures, Semmes-Weinstein monofilament testing, transcutaneous oxygen pressure (TcPO2), and vibration perception threshold assessment
other diagnostic tests, such as laboratory values, bacterial swab cultures, tissue cultures, skin biopsies, and radiologic and vascular studies.
TRACKING LABORATORY VALUES
Laboratory values can be used to evaluate and monitor chronic underlying medical conditions and to determine the patient’s nutritional status. These values should be assessed on the first patient visit to establish a baseline for care. In addition, if healing hasn’t occurred as expected, certain laboratory values can be monitored to ensure that local and systemic factors aren’t contributing to poor healing. Important parameters to evaluate include protein levels, complete blood count, erythrocyte sedimentation rate, liver function tests, glucose and iron levels, total lymphocyte count, blood urea nitrogen and creatinine levels, lipoprotein levels, vitamin and mineral levels, and urinalysis. (See Monitoring selected laboratory values, page 111.) Even if only one deterrent is present, healing can’t occur.
Pressure ulcers
Careful interpretation of a number of laboratory values can help the clinician accurately manage a patient with a pressure ulcer. Because the results of many laboratory assays, such as albumin, are affected by hydration status, tests should be repeated after a patient has been rehydrated. Current laboratory test data must be used to provide the most accurate information on the patient’s condition.
Common laboratory tests to consider in patients diagnosed with pressure ulcers include albumin, prealbumin, hemoglobin A1C, glucose, and complete blood count. Additional tests may be performed based on the patient’s overall condition.
Albumin
Albumin is a protein that acts as a building block for cells and tissues. It’s produced by the liver and, therefore, may be reduced in patients with liver disease. The albumin level is also diminished in patients with renal disease, malnutrition, severe burn wounds, and malabsorption syndromes. Adequate intake of protein and essential nutrients is necessary to ensure adequate production of albumin.
Monitoring selected laboratory values
Listed below are laboratory tests that can help assess the patient’s condition during wound and skin therapy. Levels should be monitored, as appropriate, based on the care plan related to the clinical presentation for the patient and the wound.
Laboratory test | Normal range* |
Alanine aminotransferase | 10-40 units/L |
Albumin | 3.5-5.5 g/dL |
Alkaline phosphatase | 90-130 units/L |
Aspartate aminotransferase | 10-40 units/L |
Blood urea nitrogen | 8-25 mg/dL |
Calcium | 9-11 mg/dL |
Cholesterol | 100-200 mg/dL |
Copper | 70-140 mcg/dL |
C-reactive protein | 2.6-7.6 mcg/dL |
Creatinine | 0.6-1.4 mg/dL |
Erythrocyte sedimentation rate | <10 mm/hr |
Folate | 3-16 ng/mL |
Glucose | 70-120 mg/dL |
Hematocrit | 42%-52% men; 37%-48% women |
Hemoglobin | 13-18 g/dL men; 12-16 g/dL women |
Hemoglobin A1C | <6% |
Iron | 50-150 mcg/dL |
Magnesium | 1.5-2.5 mEq/L |
Prealbumin | 16-40 mg/dL |
Total protein | 5-9 g/dL |
Total lymphocyte count | 2,000 cells/mm3 |
Transferrin | 200-400 mg/dL |
Triglycerides | 100-200 mg/dL |
Vitamin A | 30-95 mcg/dL |
Vitamin B1 | 10-60 ng/mL |
Vitamin B6 | 5-30 ng/mL |
Vitamin B12 | 200-900 pg/mL |
Vitamin C | >2 mg/dL |
Vitamin E | 5-20 mcg/mL |
Zinc | 60-150 mcg/dL |
* Values vary among laboratories. | |
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