Laboratory tests play a central role in assessing a patient and orienting the diagnostic evaluation. We report a case where the discrepancy between the manual and automatic cell count gave a hint to the final diagnosis.
A 55-year-old Caucasian man, known to have hepatitis C, was admitted with acute respiratory failure secondary to acute pulmonary edema and diffuse petechial rash of the lower extremities for the previous 2 months. The initial laboratory tests showed acute renal failure (creatinine of 2.6 mg/dL). During his hospital stay, the patient had a fluctuating white blood cell count with a recorded value of 96,000 cells/mL. On a peripheral smear, the blood cell count was in the normal range. The acute renal failure was secondary to membranoproliferative glomerulonephritis secondary to essential mixed cryoglobulinemia diagnosed by biopsy. The complete blood count values, performed by Beckman/Coulter GenS, were falsely high due to precipitation of plasma cryoglobulins at room temperature. This spurious leukocytosis was previously described in several case reports, but values as high as 96,000 cells/mL were never reported.
The presence of cryoglobulins in the blood creates a clinical challenge for the interpretation of several laboratory tests. Pseudoleukocytosis secondary to cryoglobulinemia has been observed in several reported cases with white blood cell counts up to 54,000 cells/mL at room temperature and 85,600 cells/mL at 4°C. If the cryoglobulin precipitates rapidly, aggregated cryoglobulin particles may be interpreted as blood cells. We report the first patient with pseudoleukocytosis secondary to hepatitis C cryoglobulinemia with a spurious leukocytosis of 96,000 cells/mL at room temperature. Other laboratory tests could also be affected: underestimation of true erythrocyte sedimentation rate, pseudothrombocytosis and pseudolymphocytosis. The precipitation can remove the hepatitis C virus and the antibody of cryoglobulins from serum leading to a false negative result. Any discrepancy between the automated and manual white blood cell count should lead to the suspicion of cryoglobulinemia in the clinical setting.