Rate nephelometry and radial immunodiffusion compared for measuring serum prealbumin

We compared a rate-nephelometric method and a radial immunodiffusion (RID) assay for measurement of prealbumin (transthyretin) in 55 samples of serum from healthy children. The mean prealbumin concentration as measured by the Beckman Auto ICS nephelometer was 188 mg/L (range 128-350); the mean by RID was 221 mg/L (range 125-419). This difference was statistically significant by Student's t-test (p less than 0.05), but the correlation coefficient (r) was 0.95. To determine a reference interval for prealbumin in children by the Auto ICS method, we assayed samples from 93 healthy children between the ages of one day and 18 years (55 boys, 38 girls). The mean was 191 mg/L, the reference interval (mean +/- 2 SD) 109-273 mg/L. There was no significant difference in prealbumin concentrations between girls and boys (Student's t-test, p greater than 0.05). Evidently the Beckman Auto ICS method measures prealbumin in serum rapidly and accurately.