LETTER
Clinical Use of Apolipoprotein Quantitation
A. Myron Johnson, MD;
Wendy Y. Craig, MD; and
Thomas B. Ledue, BA
1 January 1995 | Volume 122 Issue 1 | Pages 69-70
TO THE EDITOR:
The recent review of plasma apolipoproteins by Rader and colleagues [1] was thorough and generally excellent. We feel, however, that several points deserve comment. First, there are now international reference materials for apo A-I and apo B [2]. Manufacturers of immunochemical reagents and their related assay kits are currently converting to the values assigned to these reference materials. Admittedly, some differences will persist among methods and laboratories, but these should be substantially reduced after everyone has converted to the new values.
Second, the authors state that the British United Provident Association (BUPA) data [4] do not support using apo A-I levels compared with HDL cholesterol levels in population-based screening for coronary heart disease. However, the study showed that these two analytes did not significantly differ in screening performance and that neither was a good screening measurement.
Third, the statements about levels of apo B and Lp(a) found in the BUPA study are incorrect. A 10% decrease in apo B levels was associated with a 22% decrease (not increase) in the coronary artery disease mortality rate, and a 10% increase in Lp(a) levels was associated with a 3% increase (not decrease) in the risk for coronary heart disease.
One of the major conclusions of the BUPA study was that none of the lipid and lipoprotein variables measured—including levels of total cholesterol, triglycerides, HDL cholesterol, apo A-I, apo B, and Lp(a)—meet reasonable standards for use in population-based screening for coronary heart disease, either alone or in combination. The main conclusion of the study was that population-wide risk reduction is more likely to be effective in reducing the incidence of coronary heart disease than is an attempt to screen for "at-risk" persons [4].
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Author and Article Information
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The Moses H. Cone Memorial Hospital; Greensboro, NC 27401-1020
Foundation for Blood Research; Scarborough, ME 04070-0190
1. Rader DJ, Hoeg JM, Brewer HB Jr. Quantitation of plasma apolipoproteins in the primary and secondary prevention of coronary artery disease. Ann Intern Med. 1994; 120:1012-25.
2. Marcovina SM, Albers JJ, Henderson LO, Hannon WH. International Federation of Clinical Chemistry standardization project for measurements of apolipoproteins A-I and B. III. Comparability of apolipoprotein A-I values by use of international reference material. Clin Chem. 1993; 39:773-81.
3. Marcovina SM, Albers JJ, Kennedy H, Mei JV, Henderson LO, Hannon WH. International Federation of Clinical Chemistry standardization project for measurements of apolipoproteins A-I and B. IV. Comparability of apolipoprotein B values by use of International Reference Material. Clin Chem. 1994; 40:586-92.
4. Wald NJ, Law M, Watt HC, Wu T, Bailey A, Johnson AM, et al. Apolipoproteins and ischaemic heart disease: implications for screening. Lancet. 1994; 343:75-9.
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