Finger Test for the Diagnosis of a Critically Ill Patient with Necrotizing Fasciitis

Necrotizing fasciitis is a life-threatening soft-tissue infection, often characterized by soft-tissue destruction, systemic toxicity, and high mortality. No single laboratory value can diagnose necrotizing fasciitis; ultimately, necrotizing fasciitis is a clinical diagnosis and therefore presents a diagnostic dilemma for many physicians. The finger probe test is useful in confirming the diagnosis when imaging studies are unobtainable or nondiagnostic.

We present the case of a 70-year-old woman presenting nonverbal and obtunded with a soft-tissue infection of the right lower extremity. The only pertinent positive vital sign was tachypnea with a respiratory rate of 22 breaths/min. Physical examination revealed nonpitting edema, cold-to-touch lower extremity, and Nikolsky-positive hemorrhagic bullae. Initial laboratory test results showed white blood cell count of 38 x 10⁹/L and lactic acid of 8.2 mg/dL. Advanced imaging was unobtainable, given the patient's worsening clinical status, and the decision was made to perform the finger probe test, which revealed absence of bleeding and presence of friable tissue and "dishwater" discharge. Consequently, the general surgery team took the patient to the operating room and performed an above-the-knee amputation and surgical debridement. Postoperative report noted nonviable tissue consistent with necrotizing fasciitis. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Necrotizing fasciitis is a life-threatening emergency that can destroy soft-tissue at a rate of 1 inch/h. When imaging is unobtainable or nondiagnostic, the finger probe test can be used in select patients to aid with diagnosis.