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March 18, 1974

Screening Reagent for Hemoglobin S (Hb S)

Author Affiliations

University of Tennessee Memphis

JAMA. 1974;227(11):1262-1263. doi:10.1001/jama.1974.03230240020016

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To the Editor.—  Numerous screening modifications of the phosphate solubility test for hemoglobin S (Hb S) have been described (US Patent No. 3,492,095, 1970; J Clin Pathol 23:781, 1970 and 24:91, 1971; Am J Clin Pathol 58:11, 1971 and 59:300, 1973; Clin Chem 17:1028 and 1087, 1971; Summary Reports, ASCP, vol 8, August 1971; N Engl J Med 286:1143, 1972). All the reagents contain varying proportions of potassium phosphate buffer (KH2PO4 and K2HPO4), saponin (lysing agent), and sodium dithionite (Na2S2O4, reducing agent). All are based on Itano's principle (1953) that 2.24 M phosphate selectively precipitates reduced Hb S. Yet, no adequate directions have so far been given for preparation and avoidance of pitfalls.Difficulties of preparation include (1) absorption of moisture from the air by K2HPO4, causing weighing errors, transition to pyrophosphate on heating, and formation