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AACC 50th Anniversary Retrospective |
1
Department of Medicine, Weill Medical College, of Cornell University, New York, NY 10021,
2
Division of Environmental Health, Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA 30341-3724
a Address correspondence to this author at: c/o Jesse Jou, Weill Medical College of Cornell University, 445 East 69th Street, Olin Hall, Room 205, New York, NY 10021. Fax 212-746-8200; e-mail jjou{at}mail.med.cornell.edu.
In 1998 the AACC celebrates its 50th anniversary. Thus, we are honored to call attention to the outstanding professional contributions of the journal Clinical Chemistry over the years by pointing out the citation classics that have been published in its pages. By the end of 1995, 31 articles in Clinical Chemistry had been cited more than 300 times (1). Thirty of these articles were still being cited in 1995, and some are still cited to the present day. These 31 papers are distributed in multiple areas of biological sciences, and in particular: lipids, 8 papers (2)(3)(4)(5)(6)(7)(8)(9); endocrinology, 2 papers; clinical enzymology, 4 papers; intermediary metabolism, 6 papers; renal function, 2 papers; cancer, 1 paper; and calcium metabolism, 3 papers. Publications on methodology research and laboratory applications of lipid, lipoprotein, and apolipoprotein measurements in clinical investigations and epidemiologic trials have had a major impact on research of lipid metabolism and cardiovascular medicine (2)(3)(4)(5)(6)(7)(8)(9). The combined efforts of epidemiologists, clinicians, and laboratorians have produced classic publications on the understanding of lipid metabolic disorders, have stimulated development of new novel equipment and methodology, and have helped to establish the development of beneficial preventive and control measures for diseases of the heart and blood vessels.
The cited lipid papers published in Clinical Chemistry
included mainly the original papers on measurement of lipoproteins,
enzymatic measurements of cholesterol and triglycerides, and
immunoassays of apolipoproteins. The method used most widely today for
estimation of the concentration of LDL-cholesterol (LDL-C) in both
clinical and research laboratories arose from the publication of
Friedewald et al. (2) that showed that the serum
concentration of LDL-C can be estimated from available established
measurements of total cholesterol (TC), HDL-cholesterol (HDL-C), and
triglyceride (TG) in serum (Fig. 1
.). Prior to this, only time-consuming and expensive
ultracentrifugal measurements were used to determine LDL-C in serum.
The ability to calculate LDL-C thus permitted greater worldwide access
to LDL-C estimates and allowed for the greater application of the more
sensitive and specific LDL-C estimates in lieu of, or in conjunction
with, TC in the assessment of coronary heart disease risk. The
Friedewald equation has since been used as the basis of LDL-C
estimation in several landmark trials of the clinical benefits of lipid
modification, thus demonstrating its important role in the epidemiology
of coronary heart disease.
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HDL-C has become recognized as an important independent risk factor for
coronary heart disease. Two highly cited publications in Clinical
Chemistry have contributed methods that have provided valid HDL-C
laboratory measurements for clinical and epidemiologic investigations.
Lopes-Virella et al. (5) reported the analytical performance
characteristics of three different methods for the information of lipid
laboratorians (Fig. 2
). Warnick et al. (6) published a dextran sulfate
method for quantification of HDL-C that has become a method preferred
by many research and clinical laboratories.
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Around 1960, colorimetric TG measurements were of questionable accuracy and lacked desired precision. Van Handel (8) optimized the colorimetric zeolite extraction, alcoholic KOH saponification, periodate, and chromotropic acid reagent method. He purified corn, cotton, and olive oil by shaking with ground zeolite after dissolving the oil in chloroform for use as a primary standard. A modification of this colorimetric method is the TG reference method for the Centers for Disease Control and Prevention.
A major breakthrough in cholesterol analysis resulted from development
of enzymatic reagents for analytical measurements of TC. Richmond
(7) isolated a cholesterol oxidase enzyme from a species of
Nocardia, using a surfactant for solubilizing and
ion-exchange chromatography for purifying the cholesterol-oxidizing
enzyme. He determined the stability, substrate specificity, and optimal
conditions under which the enzymatic oxidation reaction could occur and
later combined alkaline ethanolic hydrolysis, enzymatic oxidation, and
colorimetric estimation for automation of the total cholesterol
analysis. Allain et al. (3) developed an automated method
for total serum cholesterol using three enzymes (Fig. 3
): cholesteryl ester hydrolase was used for hydrolysis of
cholesteryl esters, cholesterol oxidase for oxidation of cholesterol to
form hydrogen peroxide, and peroxidase for oxidative coupling to
develop color with 4-aminoantipyrine and phenol. Allain et al.
(3) also developed assays for standardization of the enzymes
for optimization experiments. These enzymatic cholesterol measurements
are applicable to measurements of low cholesterol concentrations of
HDL-C in serum.
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Bucolo and David (4) improved the TG ultraviolet test by
using a lipase together with a protease to replace chemical hydrolysis
for formation of glycerol from the TG (Fig. 4
). The determination of glycerol by the enzymatic method with
three coupling enzymes, glycerol kinase, pyruvate kinase, and lactic
dehydrogenase, measured the decrease in the absorbance of NADH at 340
nm. This procedure became the most popular ultraviolet technique for
measurement of the glycerol freed from TG because it could be used with
most manual and automated laboratory instruments.
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The development of immunochemical procedures permitted laboratory measurements of apolipoprotein (apo). In the cited article by Curry et al. (9), electroimmunoassay was applied to the measurement of apo A without requiring the use of a radioisotope in the assay. apo A and its components apos A-I and A-II are quantified by electrophoresis of the antigen into agarose containing its corresponding antibody, a process that yields precipitates that resemble ascending rockets. Washed antigen-antibody precipitates are stained with lipid stains. This electroimmunoassay along with developed immunonephelometric assays became widely used across the United States to describe complexes, associations, and reference values for different apos.
Outstanding scientific articles continue to be published in and cited from Clinical Chemistry. The Institute for Scientific Information reported that in 1996, Clinical Chemistry was cited 14 144 times, mostly in general medical and specialty journals, and had an impact factor of 3.422, which was double that of the nearest journal in the same category. Lipid articles cited widely by investigators in the cardiovascular lipid discipline recognize the following as great laboratory contributions: (a) reference methods developed by the Lipid Research Clinics (10)(11)(12) and the CDC (13); (b) development of definitive methods by NIST for cholesterol (14) and TG (15); (c) quality-control procedures for lipid determinations used widely to confirm whether methods meet analytical performance recommendations of the National Cholesterol Education Program (16)(17); (d) WHO-IFCC First International Reference Reagents for apos A-I and B developed by the IFCC Committee on Apolipoproteins in cooperation with ~30 manufacturers of apo diagnostic products (18); (e) development of remarkably precise analytical instrument systems for lipid measurements since the first automated system produced by Skeggs (19); (f) the influence of the oxidation of LDL-C on incorporation into plaques on coronary vessel walls (20); (g) the powerful cholesterol-lowering effect of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (HMG-CoA reductase inhibitors, or statins) (21); and (h) identifying and documenting new risk factors beyond those associated with lipid concentrations (22).
In the future, Clinical Chemistry will be an excellent journal in which to explore important new coronary risk factors, such as homocysteine and lipoprotein remnants. The precise mechanisms whereby lipid-lowering drugs exert their antiatherogenic effects in the arteries, particularly how statins help prevent heart attacks and stroke, will also need to be addressed. Quantitative measurements of oxidized lipids and lipoproteins may help elucidate the relationship between these particles and endothelial dysfunction, inflammation, and atherosclerosis. Laboratory measurements of lipid risk factors will be aided by mass spectrometric methods to provide improved reference materials. Homogeneous methods will keep improving automated methods for lipid measurements for clinical and epidemiologic investigations. Inflammation and infectious disease sources of coronary disease risk will be detected and documented. Research on gene therapy also shows promise of producing exciting ways to reverse atherosclerosis. For example, in the laboratory of Weill Medical College of Cornell University, gene therapy has been used to induce new blood vessel formation in a pig model of total arterial occlusion, thus restoring impaired blood flow completely.
Without doubt, Clinical Chemistry will continue to be a highly desirable forum for publications by laboratories, clinicians, and epidemiologists of the scientific results of methodology research and collaborative laboratory, clinical, and epidemiologic studies. Although the achievements of the Journal have been excellent, we predict that its future contributions and continued commitment to the field of lipid and atherosclerosis research will be even more impressive.
References
The following articles in journals at HighWire Press have cited this article:
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  E. T. Bairaktari, K. I. Seferiadis, and M. S. Elisaf Evaluation of Methods for the Measurement of Low-Density Lipoprotein Cholesterol Journal of Cardiovascular Pharmacology and Therapeutics, January 1, 2005; 10(1): 45 - 54. [Abstract] [PDF]
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 R. Rej Clinical Chemistry through Clinical Chemistry: A Journal Timeline Clin. Chem., December 1, 2004; 50(12): 2415 - 2458. [Abstract] [Full Text] [PDF]
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