Clinical associations of an increased transthyretin band in routine serum and urine protein electrophoresis.

The 9697 electrophoretograms performed over an 8 year period were reviewed to identify the frequency and clinical associations of the finding of a prominent transthyretin band in serum or urine, the concentration of which was equal to or greater than a 64 mg/dL protein calibrator. All samples were electrophoresed at a constant 90 V using agarose gels with a barbital buffer pH 8.6 and Ponceau S staining. Reference calibrators were used as standards to identify increased transthyretin bands and the patients' clinical records were subsequently reviewed. High values were found in 46 patients' sera and a further nine patients' urines representing 0.57% of the total workload. Renal impairment was present in 58% of cases including those with chronic renal failure, the nephrotic syndrome and paraproteinaemia. The high levels were not persistent in three myeloma cases where there was a recovery in renal function following chemotherapy. In some nephrotics, a high urine transthyretin may be secondary to a general hepatic albumin and transport protein synthesis response to severe proteinuria. Why the serum transthyretin was elevated in many other cases remains unclear.