| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Letters to the Editor |
Departments ofR1 Pathology and R2 Pediatrics, New York University School of Medicine, and Bellevue Hospital Center, New York, NY 10016
aAuthor for correspondence.
To the Editor:
We would like to thank Hoyer and Scheidt for their interest in our report (1), and we wish to comment on points raised in their letter.
Our report detailed the experience of a prospective study of more than 60 000 samples in a clinical laboratory, rather than a reference/research laboratory, with its use of HPLC. An algorithm involving retention time, percentage of hemoglobin fraction, and peak characteristics was proposed to aid in the processing of future samples. This algorithm has now been tested in more than 26 000 samples. Preliminary results have been presented (2), and a final manuscript is in preparation.
Hoyer and Scheidt state that the retention time can change with different lots of columns and reagents on the Variant system, which has also been reported elsewhere (3), and they give examples of retention time ranges for 3 variants from their 10-year experience. Our analysis of the retention times for hemoglobin (Hb A0), Hb A2, and Hb S showed no statistical difference over a 32-month period during which we used 3 different lots of columns and 10 different lots of reagents on the Variant II. Although we agree with Hoyer and Scheidt that the range in retention times of hemoglobin variants that they experienced may be attributable to manufacturing changes over a long time period, these changes also may be attributable to the different performance characteristics of the HPLC systems involved. Furthermore, it appears to us that the calculated SD for the retention time ranges for Hb D-Los Angeles, Hb Korle-Bu, and Hb D-Iran (0.035, 0.040, and 0.048 min, respectively) provided by Hoyer and Scheidt are nonetheless consistent with the range reported in our study (0.026 ± 0.016 min).
In Table 1 of their letter, Hoyer and Scheidt list examples of hemoglobin variants, not seen in our series, that eluted in the Ao, A2, S, and D windows. There is no doubt that other hemoglobin variants elute in these and other windows, and it would be of considerable interest to know what the incidence and clinical and hematologic impacts of these other variants are. In fact, we urge Hoyer and Scheidt to publish their experience with such a large database of retention times of common and rare hemoglobin variants along with any algorithm used in their laboratory. We believe this would be a valuable contribution to the literature on the use of HPLC in the clinical laboratory.
Finally, Hoyer and Scheidt state that some of our data were published without their knowledge or consent. Although this is true, it was the result of an unfortunate misunderstanding and was not malicious in intent. Certain specimens were forwarded to the Mayo Medical Laboratories for confirmation, as stated in our publication, through Quest Diagnostics. Additional testing was performed by isoelectric focusing, globin chain electrophoresis, and screening for unstable hemoglobins where appropriate. DNA sequence analysis was performed on 8 specimens for the definitive identification of a difficult or rare hemoglobin. We assumed that because the tests were performed on a fee-for-service basis and we had not specifically requested the DNA sequence analysis, we were not obligated to acknowledge the Mayo Medical Laboratories more that what was done in our publication. Although the report did state that the DNA sequence analysis was performed on a "research basis", we interpreted this statement, as many of our colleagues believe logically, to be a disclaimer that care should be taken in interpreting the results because of the research nature of the methodology used to ascertain the results. The Mayo Medical Laboratory report has subsequently been altered to clarify that DNA sequencing is performed under an Institutional Review Board-approved research protocol and that results may not be published in any form without the consent of the laboratory director.
We feel that there is a need for further dialogue on the proper use of HPLC in the clinical laboratory, possibly starting with the formation of local and national users’ groups. It is our hope that method-specific guidelines, recommendations, and standards can be developed to assist the clinical laboratory in the proper use of HPLC as a diagnostic tool. This can be achieved, however, only when the reliability and performance characteristics of this methodology have been fully determined.
References
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
