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SUMMARY. 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 0'57l1Jo 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. Additional key phrases: chronic renal failure; nephrotic syndrome; paraproteinaemiaA transthyretin (formerly prealbumin) band may be seen migrating towards the anode ahead of albumin with good quality electrophoresis systems but it is usually not visualized in routine serum protein electrophoretograms using agarose gels or cellulose acetate membranes, and its low serum concentration is not quantifiable by densitometry. Zone electrophoresis is used to detect the specific pathological changes found with paraproteins, and with clinically significant o l-antitrypsin deficiency. It is also used as a screen for paraproteins, for detecting protein changes in liver disease and in the quantitation of monoclonal immunoglobulins where immunochemica1methods overestimate the level of pathological protein.l-' However, with the availability of quantitative kits for specific protein measurement, zone electrophoresis now has little to offer other than the identification and quantitation of paraproteins.Transthyretin is used in nutritional assessment3.4 and is a negative acute phase reactant.

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