- Email: [email protected]
Response to “Letter to the Editor regarding a paper about HbA2 measurements on patients with HbS”
Available online at www.sciencedirect.com
Clinical Biochemistry 41 (2008) 446
Reply to Letter to the Editor Response to “Letter to the Editor regarding a paper about HbA2 measurements on patients with HbS” In response to the rebuttal letter we would like to raise the attention of the author(s) to the following: 1: We acknowledge that electrophoretic methods are not so accurate, as we also point out in the paper (first paragraph of the Discussion section): “The most serious drawback of gel-based methods is in the quantification of the separated fractions, which is performed by scanning and densitometry, procedures that are inherently not so accurate. HPLC techniques are the most reliable methods…” 2: We want to stress out that the gel electrophoresis method was used in this case because of the problem of interference by HbS when determining %HbA2 levels. HbS presence renders HPLC methods inaccurate, whereas electrophoretic methods are not affected. We agree with the authors that gel electrophoresis cannot be used as the reference method when comparing methods. However, a simple comparison of methods was not our aim (The title of the paper is: “Effect of HbS…”and not “Comparison of …”), but the quantitation of a problem deriving from HbS presence in HPLC. In our lab we also use HPLC for routine determination of HbA2, reserving gel electrophoresis for special cases. Unfortunately, the use of mass spectrometry has not yet reached the point of routine use in the clinical laboratory. 3: Regarding the possible glycation of HbS, we were not aware of this paper at the time of writing and we thank the author(s) of the letter for bringing it to our attention. However, the reasons mentioned in our paper are stated as probable, and not as definitive explanations.
4: According to [1], in homozygous sickle-cell disease HbF is 1–20% and in HbS/β0-thalassemia 5–20%. It also states: “This disorder (HbS/β0-thalassemia) clinically and hematologically resembles sickle-cell disease. The main difference is that in HbS/ β0-thalassemia, the MCV and MCH are lower and the HbA2 is increased. Family study is often necessary for a clear distinction” (page 647). Also according to [2], “In sickle-cell anemia … the hemoglobin consists of HbS and HbA2 with variable levels of HbF, ranging from a few percent to over 25%...” (page 113) and “The level of HbF in sickle-cell thalassemia is also very variable … and means of 4.3 and 7.3% for males and females, respectively, in sickle-cell β0-thalassemia…” (page 406). Under this perspective we agree with the person(s) signing the rebuttal letter, regarding the precision of electrophoretic methods. We close under the understanding that the issues raised therein were due to miscomprehension and not disagreement.
References [1] Henry John Bernard, editor. Clinical diagnosis and management by laboratory methods-19th ed. W.B. Saunders Company; 1996. [2] Weatherall DJ, Clegg JB, editors. The Thalassemia Syndromes. 4th edition. Blackwell Science Ltd; 2001.
Kostas Anagnostopoulos Laboratory of Biochemistry, Department of Medicine, Democritus University of Thrace, University Campus, 68100 Alexandroupolis, Greece E-mail addresses: [email protected], [email protected]. Fax: +30 25510 30502.
0009-9120/$ - see front matter © 2007 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.clinbiochem.2007.12.002
Clinical Biochemistry 41 (2008) 446
Reply to Letter to the Editor Response to “Letter to the Editor regarding a paper about HbA2 measurements on patients with HbS” In response to the rebuttal letter we would like to raise the attention of the author(s) to the following: 1: We acknowledge that electrophoretic methods are not so accurate, as we also point out in the paper (first paragraph of the Discussion section): “The most serious drawback of gel-based methods is in the quantification of the separated fractions, which is performed by scanning and densitometry, procedures that are inherently not so accurate. HPLC techniques are the most reliable methods…” 2: We want to stress out that the gel electrophoresis method was used in this case because of the problem of interference by HbS when determining %HbA2 levels. HbS presence renders HPLC methods inaccurate, whereas electrophoretic methods are not affected. We agree with the authors that gel electrophoresis cannot be used as the reference method when comparing methods. However, a simple comparison of methods was not our aim (The title of the paper is: “Effect of HbS…”and not “Comparison of …”), but the quantitation of a problem deriving from HbS presence in HPLC. In our lab we also use HPLC for routine determination of HbA2, reserving gel electrophoresis for special cases. Unfortunately, the use of mass spectrometry has not yet reached the point of routine use in the clinical laboratory. 3: Regarding the possible glycation of HbS, we were not aware of this paper at the time of writing and we thank the author(s) of the letter for bringing it to our attention. However, the reasons mentioned in our paper are stated as probable, and not as definitive explanations.
4: According to [1], in homozygous sickle-cell disease HbF is 1–20% and in HbS/β0-thalassemia 5–20%. It also states: “This disorder (HbS/β0-thalassemia) clinically and hematologically resembles sickle-cell disease. The main difference is that in HbS/ β0-thalassemia, the MCV and MCH are lower and the HbA2 is increased. Family study is often necessary for a clear distinction” (page 647). Also according to [2], “In sickle-cell anemia … the hemoglobin consists of HbS and HbA2 with variable levels of HbF, ranging from a few percent to over 25%...” (page 113) and “The level of HbF in sickle-cell thalassemia is also very variable … and means of 4.3 and 7.3% for males and females, respectively, in sickle-cell β0-thalassemia…” (page 406). Under this perspective we agree with the person(s) signing the rebuttal letter, regarding the precision of electrophoretic methods. We close under the understanding that the issues raised therein were due to miscomprehension and not disagreement.
References [1] Henry John Bernard, editor. Clinical diagnosis and management by laboratory methods-19th ed. W.B. Saunders Company; 1996. [2] Weatherall DJ, Clegg JB, editors. The Thalassemia Syndromes. 4th edition. Blackwell Science Ltd; 2001.
Kostas Anagnostopoulos Laboratory of Biochemistry, Department of Medicine, Democritus University of Thrace, University Campus, 68100 Alexandroupolis, Greece E-mail addresses: [email protected], [email protected]. Fax: +30 25510 30502.
0009-9120/$ - see front matter © 2007 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.clinbiochem.2007.12.002