Hemoglobin C and hemoglobin O-Arab variants can be diagnosed using the Bio-Rad Variant II high-performance liquid chromatography system without further confirmatory tests.

Context: Current standards for laboratory accreditation from the College of American Pathologists state that when high-performance liquid chromatography (HPLC) is used as a screening test, all non-A, non-S abnormal hemoglobin (Hb) variants must be confirmed by an alternative method, including alkaline and acid electrophoresis.

Objective: To determine whether confirmation of Hb C and Hb O-Arab variants by an alternative method is required when using the Bio-Rad Variant II HPLC system.

Design: We reviewed 48 478 consecutive hemoglobin identification test results performed on the Bio-Rad Variant II HPLC system during the period November 15, 2000 to January 15, 2003.

Setting: Special Hematology Laboratory, Department of Pathology, Bellevue Hospital Center, New York, NY.

Main Outcome Measures: The chromatogram patterns and retention times (RTs) for specimens containing Hb C and Hb O-Arab were analyzed. We compared the results by the HPLC method with those by the confirmatory tests (alkaline and acid electrophoresis) for both variants.

Results: We identified 3668 cases of abnormal hemoglobin variants, including 660 cases of Hb C trait (17%), 5 cases of Hb O-Arab trait (0.1%), and 1 case of Hb SO-Arab (0.03%). A unique pattern of separation on the chromatogram for Hb O-Arab was revealed, presenting as 2 distinct peaks in 2 different manufacturer-defined RT windows, namely, D and C. The chromatogram for Hb C did not show the D window in any of the reviewed cases. The RT in the C window (C-RT) revealed a statistically significant difference for Hb C and Hb O-Arab (5.18 +/- 0.01 minutes and 4.91 +/- 0.01 minutes, respectively; P <.001).

Conclusion: According to our review, the identification of Hb C and Hb O-Arab is accurate using HPLC methodology, as performed by the Bio-Rad Variant II HPLC system. This method can be both confirmatory and diagnostic at the same time.