Effect of lot-to-lot variability in filter paper on the quantification of thyroxin, thyrotropin, and phenylalanine in dried-blood specimens

W. E. Slazyk, D. L. Phillips, B. L. Therrell, W. H. Hannon

Research output: Contribution to journalArticle

26 Scopus citations

Abstract

We prepared whole-blood pools to contain various concentrations of phenylalanine (Phe), thyroxin (T4), and thyrotropin (TSH) and applied them to six different lots of Schleicher & Schuell Grade 903 filter paper, two of which represented extremes for serum-absorbancy. Individual measured T4 values showed minimal overlap among all pools for each individual filter-paper lot and for all lots combined, but Phe values overlapped considerably among the high-concentration pools within and among lots. Individual TSH values also showed considerable overlap among the high-concentration pools for all lots combined, but little overlap within each lot. Maximum differences in mean observed values among lots ranged from 6% to 36% for all analytes. Assay results from hemolyzed blood specimens generally were lower than from intact-cell blood specimens for T4 and TSH, but slightly higher for Phe. Maximum among-lot differences in mean values ranged from 13% to 29% for all analytes when each tested lot was used for assay calibration. Lot-to-lot differences in measured values were not strongly related to serum absorbancy values. We conclude that routinely encountered within- and among-lot filter paper variability, as measured by serum-absorbancy, is not alone sufficient to cause gross quantification errors in neonatal screening programs.

Original languageEnglish (US)
Pages (from-to)53-58
Number of pages6
JournalClinical Chemistry
Volume34
Issue number1
DOIs
StatePublished - 1988
Externally publishedYes

ASJC Scopus subject areas

  • Clinical Biochemistry
  • Biochemistry, medical

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