Penicillin Induced Pseudo-Hypoalbuminemia

A 75-year-old man on regular hemodialysis was admitted to our hospital with a 3-week history of low-grade fever and mild loss of appetite. The patient was ultimately diagnosed with infective endocarditis caused by Streptococcus salvarius, and treatment with a 4-week course of intravenous penicillin G 3 MU every 6 hours and a 1-week course of intravenous gentamicin was initiated. The patient’s symptoms resolved soon after treatment began; however, his serum albumin concentration, measured using a modified Bromocresol Purple (BCP) assay, fell progressively to 0.9 g/dL after 3 weeks of therapy, although serum total protein concentration remained stable. We re-measured the serum albumin concentration with a Bromocresol Green (BCG) assay, and also calculated it from the fraction of albumin in the total amount of protein assessed by electrophoresis, which yielded results of 2.7 g/dl and 2.9 g/dL, respectively. We concluded that the extremely low albumin concentration was an artifact caused by a measurement error of the modified BCP assay. The modified BCP assay is becoming an increasingly popular means of measuring albumin concentration, but there are reports that it underestimates albumin concentration in the presence of high concentrations of penicillin G. When evaluating a patient with hypoalbuminemia who is treated with penicillin G, clinicians should take into account the assay used at their institution, and, if the modified BCP assay is used, should confirm the result with other assays.