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Clinical Chemistry 43: 1098-1099, 1997;
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(Clinical Chemistry. 1997;43:1098-1099.)
© 1997 American Association for Clinical Chemistry, Inc.

Letters

Pitfalls in Discriminating Sulfhemoglobin from Methemoglobin

Paul Demedts, Annick Wauters, Mirjam Watelle and Hugo Neelsa

Lab. of Clin. Chem. and Toxicol., AZ Middelheim, Lindendreef 1, 2020 Antwerp, Belgium
a Author for correspondence.


To the Editor:

Zoppi et al. (1) recently described a case of sulfhemoglobinemia. The exact cause of the dyshemoglobinemia in this patient was not clearly mentioned, but it was probably drug-induced. The patient was improperly treated with methylene blue, on the basis of an analysis of whole blood by CO-oximetry in which the presence of methemoglobin was reported. The authors did not specify the type of CO-oximeter used for the initial analysis. However, from the tabulated data the reader is apt to conclude that the measurement was done on an IL 482 instrument (Instrumentation Laboratory, Milan, Italy).

The IL 282 and IL 482 CO-oximeters have not been constructed for determination of sulfhemoglobin. Nevertheless, these instruments can give a strong indication of the presence of sulfhemoglobin in a blood sample on the basis of a combined positive result for methemoglobin and a negative value for carboxyhemoglobin. This bizarre phenomenon was first observed by Zwart et al. and published in an evaluation report of the IL 282 CO-oximeter in 1981 (2). In the IL 282 and IL 482 operator's manuals, it is mentioned that these instruments were not constructed for the determination of sulfhemoglobin and that sulfhemoglobin may interfere with the determination of methemoglobin. The wording of the statement, however, may be unclear: "The spectral absorbance of sulfhemoglobin is similar to that of methemoglobin and the same limitations would apply. Sulfhemoglobin is not commonly found in blood, however, making such interference rare." We would favor wording such as: "The spectral absorbance of sulfhemoglobin is similar to that of methemoglobin. Therefore, the presence of sulfhemoglobin in a blood sample will cause a positive interference or false-positive result for methemoglobin. The presence of sulfhemoglobin in a blood sample is suspected whenever a methemoglobin result is displayed >=10%, combined with a negative carboxyhemoglobin value." IL now markets the model 682 CO-oximeter, which will detect and actually indicate sulfhemoglobin concentrations >1.5%, making this clarification in the new instrument's manual unnecessary. However, manufacturers could help users if they clearly mention all known clinically relevant limitations in instrument manuals and update the manuals with all essential information published in the scientific literature.


References

  1. Zoppi F, Brenna S, Fumagalli C, Marocchi A. Discrimination among dyshemoglobins: analytical approach to a toxicological query. Clin Chem 1996;42:1300-1302. [Free Full Text]
  2. Zwart A, Buursma A, Oeseburg B, Zijlstra WG. Determination of hemoglobin derivatives with the IL 282 CO-oximeter as compared with a manual spectrophotometric five-wavelength method. Clin Chem 1981;27:1903-1907. [Abstract/Free Full Text]



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This Article
Right arrow Extract Freely available
Right arrow Full Text (PDF)
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the Editor about this paper
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
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Right arrow Download to citation manager
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Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (4)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Demedts, P.
Right arrow Articles by Neels, H.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Demedts, P.
Right arrow Articles by Neels, H.
Related Collections
Right arrow General Clinical Chemistry
Right arrow Hematology

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