Mosca et al.: Commutability of controls
method calibrators only for those pairs of methods for which commutability has been proven, we strongly sug- gest that, also in the case of glyHb measurement, the commutability of calibrators and controls should be tested before the materials are used in routine methods. We also propose that manufacturers clearly state that their own materials are intended for users of their products only, unless commutability studies haven proven their com- mutability with other methods. Moreover, we think that the criterion of not exceeding 3 normalized residuals from the regression line of patient samples could be acceptable for control materials. However, a more strin- gent criterion should be used for the acceptance of cali- brators, and our data seem to indicate that 1 normalized residuals is a more appropriate criterion in such cases. Finally, it is essential that the IGSP proceeds, since the intermethod calibration of some techniques (i.e., the im- munochemical methods) by common commercially avail- able calibrators may not succeed in harmonizing the glyHb results to a clinically useful degree.
We gratefully acknowledge A. Croce (H. Civile, Abbiate- grasso, Milano), C. Franzini (H. L. Sacco, Milano), E. Guagnellini (H. S. Paolo, Milano), and M. Plebani (H. Civile, Padova) for taking part in method comparisons. We thank A. Trapolino (Dip. Sc. Tecnologie Biomediche, Milano) and V. Agape (IRCCCS H. S. Raffaele, Milano) for their skillful help. Finally, we thank Abbott, Bayer, Bio- Rad, Boehringer, Menarini, and Roche for providing us their control materials as a generous gift. This work was partially supported by a grant from M.U.R.S.T. (aliquot 60%, A.M. recipient).
References 1. Rej R. Accurate enzyme activity measurements. Two decades of development in the commutability of enzyme quality control mate-
rials. Arch Pathol Lab Med 1993;117:352–64. 2. Gubern G, Canalias F, Gella FJ. Determination of
Miedema K. Electrospray mass spectrometry for measurement of glycohemoglobin [Editorial]. Clin Chem 1997;43:705–7.
Kobold U, Jeppsson J-O, D¨ulffer T, Finke A, Hoelzel W, Miedema K. Candidate reference methods for hemoglobin A1c based on pep- tide mapping. Clin Chem 1997;43:1944–51.
Weykamp CA, Penders TJ, Muskiet FAJ, van der Slik W. Evaluation of a reference material for glycated haemoglobin. Eur J Clin Chem Clin Biochem 1996;34:67–72.
Mosca A, Paleari R, Trapolino A, Capani F, Pagano G, Plebani M. A re-evaluation of glycohemoglobin standardisation: the Italian experience with 119 laboratories and 12 methods. Eur J Clin Chem Clin Biochem 1997;35:243–8.
U.S. Department of Health and Human Services, Public Health Service. Laboratory methods for detecting hemoglobinopathies. Centers for Disease Control, Atlanta, GA 30333, September 1984:45–58.
Fairbanks VF, Klee GG. Biochemical aspects of hematology. In: Tietz NW, ed. Fundamentals of clinical chemistry, 3rd ed. Phila- delphia: WB Saunders Co., 1987:803–6.
Feldmann U, Schneider B, Klinkers H, Haeckel R. A multivariate approach for the biometric comparison of analytical methods in clinical chemistry. J Clin Chem Clin Biochem 1981;19:121–37.
Tiran A, Pieber T, Tiran B, Halwachs-Baumann G, Dobnig H, Grubelnig H, et al. Automated determination of glycated hemoglo- bin: comparative evaluation of five assay systems. J Clin Lab Anal 1994;8:128 –34.
Turpeinen U, Kajalainen U, Stenman U. Three assays for glyco- hemoglobin compared. Clin Chem 1995;41:191–5.
Eckfeldt JH, Reed R. CAP surveys. Glycohemoglobin 1996. Set GH2-A. Northridge, IL: CAP, 1996.
Tanaka S, Aoki Clark L. An assay for hemoglobin A1c testing. Am Clin Lab 1995;11:A120–3.
Wilson DH, Bogacz JP, Forsythe CM, Turk PJ, Lane TL, Gates RC, Brandt DR. Fully automated assay of glycohemoglobin with the Abbott IMx® analyzer: novel approaches for separation and detec- tion. Clin Chem 1993;39:2090–7.
Grey V, Perlas M, Aebi C. Immunoturbidimetric method for deter- mination of hemoglobin A1c [Letter]. Clin Chem 1996;42:2046–7.
Karl J, Burns G, Engel WD, Finke A, Kratzer M, Rollinger W, et al. Development and standardization of a new immunoturbidimetric Hb A1c assay. Klin Lab 1993;39:991–6.
Eckfeldt JH, Bruns DE. Another step toward standardization of
activity: methods comparison and commutability study of several control materials. Clin Chem 1995;41:435–8.
Arcangeli L, Cueroni P, Franzini C, Galletta G, Moschini A, Scapel- lato L. Inter-method differences in the measurement of some specific plasma proteins: commutability of control materials. Eur J Clin Chem Clin Biochem 1996;34:37–42.
Franzini C, Luraschi P. Commutability of control materials in cholesterol measurement. Scand J Clin Lab Invest 1993;53:51–5.
Moss DW, Whitcher JT. Reference materials and reference mea- surement systems in laboratory medicine. Commutability and the problem of method-dependent results. Eur J Clin Chem Clin Biochem 1995;33:1003–7.
Diabetes Control and Complications Trial Research Group. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent dia- betes mellitus. N Engl J Med 1993;329:977–86.
Hoelzel W, Miedema K. Development of a reference system for the international standardization of Hb A1c/glycohemoglobin determi- nations. J Int Fed Clin Chem 1996;9:62–7.
methods for measuring hemoglobin A1c 43:1811–3.
[Letter]. Clin Chem 1997;
John WG. Performance of glycated hemoglobin analysis: data from the UK national external quality assessment scheme (UK NEQAS). Biochim Clin 1989;13(s1/8):253.
Gillery P, Labbe’ D, Dumont G, Vassault A. Glycohemoglobin assays evaluated in a large-scale quality-control survey. Clin Chem 1995;41:1644 – 8.
Sampson EJ, Duncan PH, Fast DM, Whitner CS, McKneally SS, Baird MA, et al. Characterization and intermethod relationships of materials containing purified human pancreatic and salivary amy- lase. Clin Chem 1981;27:714–20.
Gould BJ, Mosca A, Miedema K, Colinet E, Profilis C. The determination of Hb A1c (glycated hemoglobin) in a human haemolysate reference material. Commission of the European Communities, Community Bureau of Reference, Directorate- General Science, Research and Development, EUR 15136EN, Brussels, Luxembourg 1993.