Introduction: 5-Fluorouracil is a commonly prescribed antineoplastic drug. Historically, methods ... more Introduction: 5-Fluorouracil is a commonly prescribed antineoplastic drug. Historically, methods to determine this compound in biological fluids have been time consuming or not sensitive enough.
Serum creatinine and total protein are routinely measured biochemical parameters used in clinical... more Serum creatinine and total protein are routinely measured biochemical parameters used in clinical medicine. An abnormal result caused by interference with the assay does not accurately reflect a patient’s clinical state and therefore risks misleading clinicians. We report the case of a patient who had unexplainable high creatinine and total protein results. The blood collection was contaminated with intravenous fluid and the patient was receiving piperacillin/tazobactam. Additional laboratory studies demonstrated piperacillin/tazobactam was the cause of the false positive results and the elevation in both serum creatinine and protein level was dependent on the concentration of antibiotic present.
Measurement of serum free light chains (FLC) is useful for the diagnosis and monitoring of monocl... more Measurement of serum free light chains (FLC) is useful for the diagnosis and monitoring of monoclonal light-chain diseases. It has been suggested that there will be widespread replacement of urine Bence Jones protein measurement by serum FLC assay. We report on our experience with the assay during monitoring of light-chain myeloma (LCMM) and AL amyloidosis (AL). Serum FLC immunoassay, serum and/or urine protein electrophoresis and immunofixation were performed on serial samples during monitoring of LCMM. Recovery and immunoreactivity of FLC were tested by sample dilution. Assay precision was determined by repeat assay of samples over several reagent lots. In one of 23 patients with LCMM there was non-reaction of a monoclonal kappa FLC with some reagent lots and the assay did not indicate disease relapse. Samples showed non-linear, non-parallel immunoreactivity on dilution. Several tested monoclonal FLC gave lower values at the assay starting dilution compared with higher sample dilution and non-parallel dose-response curves. The median between-reagent lot variation for FLC measurement was 19-20% CV. Laboratory staff and clinicians need to be aware of the potential for non-reactivity of individual monoclonal FLC, and the effects of dilution and precision on FLC values and their interpretation.
Introduction: 5-Fluorouracil is a commonly prescribed antineoplastic drug. Historically, methods ... more Introduction: 5-Fluorouracil is a commonly prescribed antineoplastic drug. Historically, methods to determine this compound in biological fluids have been time consuming or not sensitive enough.
Serum creatinine and total protein are routinely measured biochemical parameters used in clinical... more Serum creatinine and total protein are routinely measured biochemical parameters used in clinical medicine. An abnormal result caused by interference with the assay does not accurately reflect a patient’s clinical state and therefore risks misleading clinicians. We report the case of a patient who had unexplainable high creatinine and total protein results. The blood collection was contaminated with intravenous fluid and the patient was receiving piperacillin/tazobactam. Additional laboratory studies demonstrated piperacillin/tazobactam was the cause of the false positive results and the elevation in both serum creatinine and protein level was dependent on the concentration of antibiotic present.
Measurement of serum free light chains (FLC) is useful for the diagnosis and monitoring of monocl... more Measurement of serum free light chains (FLC) is useful for the diagnosis and monitoring of monoclonal light-chain diseases. It has been suggested that there will be widespread replacement of urine Bence Jones protein measurement by serum FLC assay. We report on our experience with the assay during monitoring of light-chain myeloma (LCMM) and AL amyloidosis (AL). Serum FLC immunoassay, serum and/or urine protein electrophoresis and immunofixation were performed on serial samples during monitoring of LCMM. Recovery and immunoreactivity of FLC were tested by sample dilution. Assay precision was determined by repeat assay of samples over several reagent lots. In one of 23 patients with LCMM there was non-reaction of a monoclonal kappa FLC with some reagent lots and the assay did not indicate disease relapse. Samples showed non-linear, non-parallel immunoreactivity on dilution. Several tested monoclonal FLC gave lower values at the assay starting dilution compared with higher sample dilution and non-parallel dose-response curves. The median between-reagent lot variation for FLC measurement was 19-20% CV. Laboratory staff and clinicians need to be aware of the potential for non-reactivity of individual monoclonal FLC, and the effects of dilution and precision on FLC values and their interpretation.
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