Optimal Assay of LDH and α-HBD at 37 °C

The optimal substrate, hydrogen ion, and coenzyme concentrations for Lactate Dehydrogenase and Alpha-Hydroxybutyrate Dehydrogenase have been established at the physiological temperature 37°C, using an LKB 8600 Reaction Rate Analyzer.

Venous thromboembolism in association with features of the metabolic syndrome

BACKGROUND

Central obesity, diabetes mellitus, dyslipidaemia and chronic hypertension--features of the metabolic syndrome--have been individually associated with venous thromboembolism (VTE). However, whether each of these factors additively increases the risk of VTE is uncertain.

AIM

To determine whether features of the metabolic syndrome independently increase the risk of VTE.

DESIGN

Prospective cohort study derived from the Heart Outcomes Prevention Evaluation 2 (HOPE-2) randomized clinical trial.

SETTING

One hundred and forty-five clinical centres in 13 countries.

METHODS

We studied 5522 adults aged > or =55 years with cardiovascular disease or diabetes mellitus. At enrollment, 35% had 0-1 features of the metabolic syndrome, 30% had two, 24% had three and 11% had four. We defined symptomatic VTE as an objectively confirmed new episode of deep-vein thrombosis or pulmonary embolism.

RESULTS

VTE occurred in 88 individuals during a median 5.0 years of follow-up. The incidence rate of VTE (per 100 person-years) was 0.30 with 0-1 features, 0.36 with two features, 0.38 with three features and 0.40 with four features of the metabolic syndrome (trend p = 0.43). Relative to the presence of 0-1 features of the metabolic syndrome, the adjusted hazard ratio (95%CI) for VTE was 1.22 (0.71-2.08) with two features, 1.25 (0.70-2.24) with three features, and 1.26 (0.59-2.69) with four features.

DISCUSSION

The number of features of the metabolic syndrome present was not a clinically important risk factor for VTE in older adults with vascular arterial disease.

The HOPE (Heart Outcomes Prevention Evaluation) Study and its consequences

The HOPE study was a 19 country, prospective randomized trial in which the ACE-inhibitor Ramipril but not Vitamin E significantly reduced the risk of future cardiovascular events in a high-risk population of men and women, including many with diabetes. The benefits were present in all sub-groups, independent of the presence or absence of diabetes, hypertension, evidence of cardiovascular disease, microalbuminuria, blood pressure lowering, the use of aspirin, lipid-lowering or antihypertensive medication. It provided clear evidence that Ramipril should safely and cost-effectively be used in individuals not known to have low ventricular ejection fraction or heart failure but at high-risk of cardiovascular events. It was also beneficial in patients with renal insufficiency, reducing progression of proteinuria and development of new microalbuminuria. It provided micro- and macrovascular benefits in people with diabetes, reduced the development of new cases of diabetes and showed a positive and graded association between the waist-to-hip ratio and the risk of developing diabetes. Sub-studies completed and on-going into the predictive role of natriuretic peptides, infectious and inflammatory markers, provide insight into possible mechanisms of action of Ramipril.

Overview of evidence-based medicine: challenges for evidence-based laboratory medicine

Evidence-based medicine (EBM) has been driven by the need to cope with information overload, by cost-control, and by a public impatient for the best in diagnostics and treatment. Clinical guidelines, care maps, and outcome measures are quality improvement tools for the appropriateness, efficiency, and effectiveness of health services. Although they are imperfect, their value increases with the quality of the evidence they incorporate. Laboratory professionals must direct more effort to demonstrating the impact of laboratory tests on a greater variety of clinical outcomes. Laboratory and clinical practitioners must be familiar with many of the accessible electronic and paper tools for searching for evidence. Detailed statistical and epidemiologic knowledge is not essential, but critical appraisal skills and a competent understanding of the strengths and weaknesses of systematic review and metaanalysis are necessary. Overemphasis on complexity and failure to recognize time limitations are major barriers to translating EBM into everyday practice. Emphasizing and practicing the role of the laboratory professional as a skilled clinical consultant strongly grounded in evidence as well, in addition to better integration of laboratory and clinical information and improved laboratory reports will overcome most barriers. There is a poverty of good, primary studies of test evaluations. Institution of more consistent standards for the design and reporting of studies on diagnostic accuracy should improve the situation. If nothing else, systematic reviews have demonstrated the need for more good-quality primary research in laboratory medicine.

The surface effect of dentifrices

The aim of this study was to evaluate clinically three commercially available dentifrices and to determine any surface effects on tooth or gingival surfaces. Sixty-four participants were included in this study and were allocated randomly to one of four treatment groups by an independent person to ensure the investigators were unaware of the brushing material used. All toothbrushes and dentifrices were distributed by this independent person. The treatment groups were: Group 1--brush with water; Group 2--brush with Colgate (Baking Soda and Peroxide); Group 3--brush with Macleans (Whitening); Group 4--brush with Colgate (Sensation Whitening). All participants were requested to brush both morning and evening in their customary fashion using only the designated toothpaste, or water, for four weeks. All participants were required to use the same toothbrush type. No other oral hygiene products such as mouth rinses or dental floss were used during the trial period. Prior to commencement of the brushing period, all participants received a full clinical examination recording the status of the soft and hard tissues including a gingival index (Löe and Silness) to record gingival condition. A polyvinyl siloxane impression was taken of the six anterior teeth and gingival tissues at the commencement of the trial. After four weeks, a second full clinical examination was made and further silicone impressions were taken of the anterior teeth. All impressions were cast in epoxy resin for investigation with light and electron microscopy. Participants were also asked to answer a questionnaire relating to the toothpaste used. The results of this study indicated that no significant clinical differences were recorded for any dentifrice or water and there was no significant difference in gingival index scores over the four week period. Patient responses to each dentifrice varied according to individual patient preferences and expectations and no consistent findings could be determined. Light and electron microscopy indicated that tooth and gingival surface changes that occurred over the four week period with any of the dentifrices were similar to, and not significantly different from, changes seen with the use of water alone. These results indicate that none of the dentifrices tested was harmful to teeth or soft tissues.

Evidence-based medicine: its application to laboratory medicine

The current health care environment of cost-cutting highlights the need to reinforce the contribution of laboratory medicine to improvement in health care. This must be a patient-focused activity using continuous quality improvement, a familiar concept in laboratory practice. Involvement in the creation of clinical practice guidelines, care maps, and outcome measures will place laboratory medicine in the circle of continuous quality improvement. The laboratory must provide strong evidence that tests contribute to better overall resource utilization. Laboratory Information Systems can be used to better integrate laboratory data with clinical, diagnostic, pharmaceutic, statistical, and financial information. Improving laboratory utilization requires clear demonstrations of appropriate versus inappropriate laboratory use, and instructions on implementing appropriate use. The education of laboratory professionals should include search strategies, understanding the diagnostic accuracy of medical tests, and the application of systematic reviews and meta-analysis. With the rapid increase in the data base supporting evidence-based laboratory medicine, there is a significant challenge in translating the existing knowledge into practice. There is also a need for a cooperative strategy between the diagnostics industry and the laboratory medicine profession to provide evidence of the added value of laboratory testing. There is a significant role in developing the academic basis of the unique aspects of evidence-based laboratory medicine.

Monthly intra-individual variation in lipids over a 1-year period in 22 normal subjects

OBJECTIVES

Previous reports on biological variation in lipids differ widely in the time interval between sampling, the number of samples analyzed per patient and the total study period. The present investigation was carried out to determine monthly intra-individual variation in lipids over 1 year and to establish whether there was a consistent change in lipid values over the summer months. The importance of taking this variation into consideration during the assessment of risk of coronary heart disease (CHD) was also examined.

DESIGN AND METHODS

Cholesterol, triglycerides, HDL, apo A1, and apo B were measured at monthly intervals for 12 months in 22 healthy, free-living volunteers (11 females, 11 males) by standardized methods.

RESULTS

When compared to analytical variation, biological variation was the dominant component of the intra-individual changes observed during the 1-year study period. As expected, triglycerides showed the greatest biological variation; the ratio of biological/analytical variation was 33.1. Much smaller ratios were observed for the other lipids measured in this study with values ranging from 4.2 to 6.8. Different subjects attained their maximum and minimum values in virtually every month of the year. There were significant reductions in cholesterol, HDL, LDL, and apo A1 in the summer months while triglycerides showed a non-significant increase and apo B a non-significant decrease during this period.

CONCLUSIONS

All the analytes showed considerable intra-individual variation. It is, therefore, important to measure lipids sequentially over several weeks to arrive at an average value for risk stratification for CHD.

Ethical and legal issues in the procurement, storage and use of DNA

At the risk of ignoring the benefits, the problems of genetic testing have been widely discussed. Many clinical laboratories are archival stores for human tissues and very few have formal policies and procedures for the use of this material. There is little evidence of planning or preparation of appropriate protocols for the safekeeping of the collected clinical material. The process of informed consent needs to be re-examined. The standard of what would be expected by a reasonable and prudent person poses challenging questions relating to confidentiality and privacy, control and ownership of the stored tissue and cells, withdrawing from a research study, length of storage of samples, the use of biological materials by other parties, and the use of biological materials for purposes other than those for which they were first obtained. There also needs to be a clear understanding of identifiable, non-identifiable and anonymous samples. Clinical laboratory staff and their professional organisations need to engage in the discussion and development around the ethical, legal and social issues raised by testing human DNA. Clinical research laboratories will be increasingly involved in DNA testing and will be asked for access to stored blood or tissue. It is essential that professional responsibility is understood and is then exercised in the presence of appropriate policies and procedures. There is also a paramount need to involve the public who are already demonstrating evidence of alienation from the world occupied by genetics research.

Cholesteryl ester transfer protein mutations, protein activity and HDL-cholesterol concentration

We have examined a group of North American subjects, selected to include individuals with a wide variety of HDL-cholesterol concentrations for: 1) mutations in the genes coding for cholesteryl ester transfer protein and hepatic lipase, 2) apolipoprotein E genotype, 3) total cholesterol and triglycerides, 4) HDL-triglycerides. Cholesteryl ester transfer protein activity was also estimated, using a novel technique that does not require separation of substrate and product. Transfer activity was shown to have a monophasic distribution, with a mean activity of 21 pmol substrate transferred/3 h/microl plasma. The cholesterol ester transfer activity of the group with HDL-cholesterol >1.60 mmol/l was significantly less than those with HDL-cholesterol <1.60 mmol/l. The cholesteryl ester transfer protein G1533A mutation was detected at an overall allele frequency of 2.91%. The mutation was more frequent in the group with HDL-cholesterol <1.60 mmol/l than in those >1.60 mmol/l. It was also more frequent in those with protein activity > 30 pmol/ 3h/microl plasma than in those with activity <30. These data suggest that this mutation in cholesteryl ester transfer protein is associated with increased transfer activity and reduced HDL-cholesterol concentrations. The cholesteryl ester transfer protein activity assay described here is simple and convenient. Subject to further evaluation and correlation with the present labour and time intensive assays, this commercially available assay offers the potential of rapid, simple analysis of large numbers of samples.

Blood lipid profiles in children with acute lymphoblastic leukemia

BACKGROUND

Abnormal blood lipid profiles have been associated with cancer. The objective of this study was to investigate the frequency and clinical significance of altered lipid profiles in children with acute lymphoblastic leukemia (ALL), the most common form of malignant disease in this age group.

METHODS

Fasting blood lipid profiles (cholesterol [C], triglycerides [TG], high density lipoprotein [HDL], low density lipoprotein, very low density lipoprotein, apolipoproteins A1 [apo A1] and B, and lipoprotein a [Lp(a)]) were obtained in 24 children with ALL at diagnosis, 16 children during consolidation therapy with L-asparaginase, and 18 children during maintenance therapy without L-asparaginase. For comparison the authors studied lipid profiles in 15 children previously treated for leukemia, 15 healthy control children, and 17 children with other forms of cancer, both localized and widespread.

RESULTS

An altered blood lipid profile was observed at the time of diagnosis of ALL. Statistically significant values included elevated TG (1.82+/-1.23 mmol/L), reduced HDL-C (0.54+/-0.24 mmol/L), and reduced ApoA1 (0.77+/-0.18 g/L) levels. A wide range of Lp(a) levels (0-1990 mg/L) were observed. Significantly reduced HDL-C (0.55+/-0.20 mmol/L) and ApoA1 (0.69+/-0.22 g/L) were observed in children with widespread but not localized solid tumors at diagnosis. C and TG correlated with serum albumin levels. Significant therapy-related changes in lipid profiles were observed in children with ALL during combination therapy with L-asparaginase (extremely elevated TG levels [3.34+/-2.82 mmol/L] and a striking reduction in Lp(a) levels) that were not observed during combination therapy without L-asparaginase or in children during treatment for solid tumors. In this small study there was no relation between these abnormalities and either thromboembolic events or pancreatitis. Blood lipid profiles in children with ALL returned to normal on completion of therapy.

CONCLUSIONS

The lipid abnormalities observed at diagnosis in children with widespread cancer (ALL or solid tumors) may reflect altered nutritional states or altered lipid metabolism. Reduced concentrations of Lp(a) and elevated TG levels suggest L-asparaginase specific alterations and may provide insight into the toxicity associated with this drug.

Laboratory quality assurance at the international level: the role of nongovernmental organizations

A wide range of nongovernmental organizations are involved in laboratory quality assurance at the international level. These organizations include for-profit organizations such as Murex or Randox, nonprofit organizations such as the Institute for Standardization and Documentation in Medical Laboratories (INSTAND), national professional organizations such as the National Committee for Clinical Laboratory Standards (NCCLS), regional organizations such as the Asian Pacific and Latin American Federation of Clinical Biochemists and International organizations such as the IFCC and WHO. The Interaction and roles of such organizations are discussed.

Reverse cholesterol transport--a review of the process and its clinical implications

OBJECTIVES

This review article will summarize the current knowledge surrounding the reverse cholesterol transport system; the process, the effect of mutations in genes coding for proteins which function in the system, and the possible clinical implications of these alterations.

RESULTS

High-density lipoprotein-cholesterol (HDL-C) concentration is a marker for the reverse cholesterol transport (RCT) system, whereby cholesterol is returned from peripheral cells to the liver for reuse or excretion in the bile. Increased HDL-C concentrations are generally accepted to be protective against the future development of atherosclerosis and coronary artery disease (CAD), but recent evidence has indicated that the underlying cause of the increased HDL-C may affect whether it is protective or detrimental. The major steps in the RCT pathway are the efflux of free cholesterol from cells and binding by pre-beta HDL, esterification of HDL-bound cholesterol by lecithin cholesterol acyl transferase (LCAT), cholesteryl ester transfer protein (CETP) mediated exchange of cholesteryl ester and triglycerides between HDL and apo B-containing particles, and hepatic lipase (HL) mediated uptake of cholesterol and triglycerides by the liver. Mutations in proteins active in the RCT pathway can shed light on the functions and control of the various steps in the system. LCAT deficiency, leading to greatly reduced HDL and fish eye disease, is not usually associated with increased risk of CAD. Several new mutations in LCAT have recently been reported, however, which do result in CAD. Mutations leading to reduced CETP activity result in less CE being directed into apo-B containing particles and more remaining in the HDL. This has been associated with increased HDL-C concentrations. The generally accepted hypothesis that reduced CETP activity leads to reduced CAD risk has been challenged by a number of recent publications, and has become an area of active investigation. Mutations leading to reduced HL activity are rare occurrences. To date, all have been associated with increased HDL-C concentrations and CAD.

CONCLUSION

The development of techniques to identify and characterize the functional significance of mutations in proteins involved in RCT will aid in the understanding of the mechanisms and control of this pathway.

Mutations in cholesteryl ester transfer protein and hepatic lipase in a North American population

OBJECTIVE

To examine a North American population sample with increased HDL cholesterol for mutations in the genes coding for cholesteryl ester transfer protein (CETP) and hepatic lipase (HL).

DESIGN AND METHODS

Seventy individuals with increased HDL cholesterol at the time of initial presentation to the Lipid Clinic (males > 1.7 mmol/L, females > 1.8 mmol/L) were examined by polymerase chain reaction-restriction fragment length polymorphism (PCR/RFLP) analysis for known mutations in CETP intron 14 and exon 15 and HL exons 6 and 8.

RESULTS

CETP intron 14 mutation frequency 0.7%, CETP exon 15 A1503G 0%, HL exon 6 C873T 2.1%, HL exon 8 C1221T 0%. An unusual mutation in CETP exon 15 G1533A was found at a frequency of 3.5%. The sequence of this mutation was determined to be a G to A change at bp 1533 resulting in a predicted amino acid change of arginine to glutamine at position 451.

CONCLUSIONS

Known mutations in CETP were much less prevalent in this North American population than in the Japanese populations that have been previously reported. HL mutations, described previously in only 6 families worldwide, appear to be more prevalent than previously recognized. CETP G1533A, reported only once previously is prevalent in this population at a surprisingly high frequency. The functional significance of this mutation is unknown.

Monthly intra-individual variation in lipoprotein(a) in 22 normal subjects over 12 months

OBJECTIVES

It is generally believe that lipoprotein(a) (Lp(a)) levels remain relatively constant in the same individual, but there is a paucity of data to substantiate this belief. This study was undertaken to determine the extent of intra-individual variation in Lp(a) over a 12-month period.

DESIGN AND METHODS

Lp(a) was measured monthly in duplicate over a 12-month period in 11 females and 11 males who were healthy, free-living, normal subjects by the Incstar Immunoprecipitin method using a goat antibody which was monospecific for Lp(a).

RESULTS

Some subjects showed considerable month-to-month variations which were not correlated with changes in other lipid parameters or with weight. Others showed fairly constant Lp(a) levels, with a few values which were quite different from the rest. This was not attributable to methodological factors; low and high controls gave mean (mg/L), SD and CV values of 181, 8.6, 4.7 and 431, 14, 3.3, respectively. The difference between the minimum and maximum values in the same individuals ranged from a low of 14 mg/L in one subject to a high of 229 mg/L in another over the one-year period.

CONCLUSIONS

Lp(a) showed greater intra-individual variations in normal subjects than is commonly believed. It is therefore recommended that Lp(a) should be measured sequentially over a few weeks to arrive at a mean value for assessing risk of coronary heart disease.

Clinical and analytical considerations in the utilization of cholinesterase measurements

Many theories have been advanced but the true physiological function for serum cholinesterase has still not been identified. Evidence has been presented for the abnormal expression of cholinesterase genes in many types of human tumors. Cholinesterase measurements are still used to monitor exposure to organophosphate insecticides and their clinical application requires a good understanding of the inter and intra-individual variation, as well as some knowledge of the time sequence between exposure and measurement of the cholinesterase activity. The use of serum cholinesterase measurement in liver disease varies in different countries. A case has not been made for the cost-effectiveness of adding serum cholinesterase as part of a screening procedure for the diagnosis of liver disease. During the last 10 years much information has been obtained on the molecular biology and genetics of acetylcholinesterase and butyrylcholinesterase, distinct enzymes encoded by two different, but related genes. It has been established that BChE is included by a single gene which corresponds to the E1 locus. The complete amino acid sequence of human serum cholinesterase and the location of disulfide bonds within the sequence have been described. The molecular basis of many variants of human serum cholinesterase has been described in detail. It is not rare for multiple mutations to occur within a single butyrylcholinesterase gene or there may be combination of mutations. At least 11 silent variants of human butyrylcholinesterase have been identified. There still exists a wide variety of substrates and analytical conditions for butyrylcholinesterase measurement in a number of clinical situations. No real evidence has been provided for clinical value for their use in the diagnosis of Alzheimer disease or monitoring the use of cholinesterase inhibitors in the treatment of pre-senile dementia of Alzheimer type. However, the insights from molecular biology technology may well open up more challenges in a variety of clinical situations.

Hamilton Health Sciences Laboratory Program: a provider developed model for hospital, university and community laboratory services

Clinical Laboratory Sciences are under pressure to reduce the number of tests and cut staff and supply costs. The ability of academic centres to continue to deliver high quality service, teaching and research is threatened. In difficult economic times imaginative strategies are needed to look for solutions which will permit continued advancement in academic and clinical standards. Rationalization of service and cost-effective use of resources are not new concepts; however, there is a scarcity of models which have been developed and promoted by the providers of laboratory services, rather than those imposed by governments and other paying agencies. A model developed and evolved over the last two decades by The Hamilton Health Sciences Laboratory Program (HHSLP) is outlined.

Is determination of creatine kinase-2 after electrophoretic separation accurate?

Since 1991, the Ontario Laboratory Proficiency Testing Program has assessed the analytical performance of creatine kinase (CK; EC 2.7.3.2) isoenzyme-2, using fresh human serum supplemented with purified human CK isoenzymes. In Ontario, the 142 laboratories licensed to analyze CK-2 use a variety of methods: electrophoresis-based, immunoinhibition, and mass assays. During a 1992 survey, duplicate CK-2 samples with different total CK activities showed poorer precision when analyzed after electrophoretic separation than by any other method. A 1993 survey designed to validate these observations conclusively showed that electrophoresis-based assays are subject to a bias proportional to the total CK activity. These survey results were confirmed by studies with selected patients' specimens. We therefore conclude that electrophoresis-based assays may not warrant their reputation as the gold standard for CK isoenzyme measurement.

Is determination of creatine kinase-2 after electrophoretic separation accurate?

Since 1991, the Ontario Laboratory Proficiency Testing Program has assessed the analytical performance of creatine kinase (CK; EC 2.7.3.2) isoenzyme-2, using fresh human serum supplemented with purified human CK isoenzymes. In Ontario, the 142 laboratories licensed to analyze CK-2 use a variety of methods: electrophoresis-based, immunoinhibition, and mass assays. During a 1992 survey, duplicate CK-2 samples with different total CK activities showed poorer precision when analyzed after electrophoretic separation than by any other method. A 1993 survey designed to validate these observations conclusively showed that electrophoresis-based assays are subject to a bias proportional to the total CK activity. These survey results were confirmed by studies with selected patients' specimens. We therefore conclude that electrophoresis-based assays may not warrant their reputation as the gold standard for CK isoenzyme measurement.

Evaluation of a turbidimetric procedure for apolipoproteins A1 and B on the Ciba Corning 550 EXPRESS

We evaluated a turbidimetric method for the estimation of apo A1 and apo B on the Ciba Corning 550 EXPRESS using Ciba Corning reagents. Interference due to bilirubin, hemoglobin, lipemia, triglycerides, and uremia was minimal, with apolipoproteins (apo) A1 and B results usually within +/- 4% of expected values. Within-run and day-to-day imprecision (coefficients of variation) ranged from 1.96 to 3.60% and 2.63 to 3.39% for apo A1 and 1.02 to 1.74% and 2.08 to 3.66% for apo B, respectively. Accuracy was determined by participation in the IFCC apolipoprotein standardization project in which results obtained on 50 patient samples were compared to those obtained by the reference laboratory. Apo A1 and apo B showed an average bias of +3.7% and +2.0% and correlation coefficients of 0.986 and 0.977, respectively. Results were also compared to those obtained on the Behring Turbitime system and showed a bias of +7.5% and -8.8% for apo A1 and apo B, respectively. The Ciba Corning automated method was rapid and gave good accuracy, precision, linearity, and parallelism and was relatively unaffected by raised triglyceride values.

Testing for Creatine Kinase and Creatine Kinase-2 in Ontario: Reference Ranges and Assay Types

In 1991, 246 and 136 Ontario laboratories performed total creatine kinase (CK; EC 2.7.3.2) and creatine kinase-2 (CK-2) assays, respectively. A questionnaire mailed to these laboratories requested information about the types of assay used, the origin of their reference ranges, and the source of their instruments and reagents. All laboratories used current test formulations for CK, although seven laboratories did not assay at 37 degrees C. For CK, 69% of all laboratories reported different upper reference limits for men and women (5th-95th percentiles: 160-250 and 115-215 U/L, respectively); 31% reported similar ranges for both sexes. Fifty-six percent derived their own ranges; the remainder used either kit inserts or literature references, and nearly 60% of this latter group claimed to have validated these suggested ranges before use. For 6% of all laboratories, their pediatric ranges were similar to their adult ranges. For CK-2, only 32% used their own reference range; the remainder used kit inserts or literature references, but only 49% of this group validated these ranges before use. Reference limits (5th-95th percentiles) for CK-2 were as follows: activity 6-24 U/L; fraction of CK, 0.022-0.06; and, for mass assays, 5-10 micrograms/L and relative index 0.015-0.04.

Testing for creatine kinase and creatine kinase-2 in Ontario: reference ranges and assay types

In 1991, 246 and 136 Ontario laboratories performed total creatine kinase (CK; EC 2.7.3.2) and creatine kinase-2 (CK-2) assays, respectively. A questionnaire mailed to these laboratories requested information about the types of assay used, the origin of their reference ranges, and the source of their instruments and reagents. All laboratories used current test formulations for CK, although seven laboratories did not assay at 37 degrees C. For CK, 69% of all laboratories reported different upper reference limits for men and women (5th-95th percentiles: 160-250 and 115-215 U/L, respectively); 31% reported similar ranges for both sexes. Fifty-six percent derived their own ranges; the remainder used either kit inserts or literature references, and nearly 60% of this latter group claimed to have validated these suggested ranges before use. For 6% of all laboratories, their pediatric ranges were similar to their adult ranges. For CK-2, only 32% used their own reference range; the remainder used kit inserts or literature references, but only 49% of this group validated these ranges before use. Reference limits (5th-95th percentiles) for CK-2 were as follows: activity 6-24 U/L; fraction of CK, 0.022-0.06; and, for mass assays, 5-10 micrograms/L and relative index 0.015-0.04.

Results of a province-wide quality assurance program assessing the accuracy of cholesterol, triglycerides, and high-density lipoprotein cholesterol measurements and calculated low-density lipoprotein cholesterol in Ontario, using fresh human serum

To evaluate laboratory performance, eight to 13 samples of fresh human serum from volunteers were sent to 250 laboratories in the Canadian province of Ontario licensed to perform lipid analysis. Fresh human specimens were used because of potential matrix effects with processed materials. We show that on all survey samples, 71% (range, 63% to 82%) of participating laboratories are within +/- 5% of the target cholesterol value and that 93% are within +/- 10%. The goal of the National Cholesterol Education Program for 1992 is total error of no more than +/- 9% for 95% of results. The unblanked triglycerides results show that on all samples 40% (14% to 59%) of participants are within +/- 5% and 68% (range, 31% to 86%) are within +/- 10% of the target value. For triglycerides results from 0.9 to 2.0 mmol/L, 80% or more are within +/- 0.2 mmol/L. Between 2.0 and 3.0 mmol/L, 90% are within +/- 0.3 mmol/L of the target values. For high-density lipoprotein cholesterol, for all samples 35% (range, 24% to 50%) of laboratories are within +/- 5% and 68% (range, 55% to 88%) are within +/- 10%. A range of 80% to 95% of participants are within +/- 0.2 mmol/L of the target values. For calculated low-density lipoprotein cholesterol, 51% and 62% of the laboratories surveyed are within +/- 5%, with 83% and 89% within +/- 10% of the target values. We conclude that the laboratory measurement of lipids is approaching the degree of accuracy and precision required for clinical purposes, and that the use of fresh human serum samples is a viable approach to their proficiency testing.

Proficiency testing for creatine kinase isoenzyme CK-2 (CK-MB) in Ontario

Three surveys of the measurement and interpretation of creatine kinase (CK; EC 2.7.3.2) isoenzyme 2 (CK-MB) were conducted in Ontario, Canada, in 1989. Of the clinical laboratories participating, 66% used immunological methods and 24% used electrophoretic methods. Although reference ranges and interpretative routines varied widely, 95% of the laboratories reported correct interpretations for 10 of the 15 vials tested. The only major problems occurred with samples with very low total CK activity. Within-survey duplicate results compared well, and 89% of the laboratories had consistent between-survey results, even for specimens with low total CK activity. Errors were proportional to the frequency of use of the different analytical methods. The lyophilized testing material gave higher results with methods for measuring the mass of CK-2, suggesting that the material contained inactive but immunologically intact CK-2. The surveys indicate that laboratories should review their protocols for measuring CK-2 when only a single sample from the patient is available.

Proficiency testing for creatine kinase isoenzyme CK-2 (CK-MB) in Ontario

Three surveys of the measurement and interpretation of creatine kinase (CK; EC 2.7.3.2) isoenzyme 2 (CK-MB) were conducted in Ontario, Canada, in 1989. Of the clinical laboratories participating, 66% used immunological methods and 24% used electrophoretic methods. Although reference ranges and interpretative routines varied widely, 95% of the laboratories reported correct interpretations for 10 of the 15 vials tested. The only major problems occurred with samples with very low total CK activity. Within-survey duplicate results compared well, and 89% of the laboratories had consistent between-survey results, even for specimens with low total CK activity. Errors were proportional to the frequency of use of the different analytical methods. The lyophilized testing material gave higher results with methods for measuring the mass of CK-2, suggesting that the material contained inactive but immunologically intact CK-2. The surveys indicate that laboratories should review their protocols for measuring CK-2 when only a single sample from the patient is available.

Ethics and laboratory medicine

Ethical issues have been given limited attention by professionals in laboratory medicine. Professional ethics is the moral bond that links a profession, the people it serves, and society. Understanding the complexities of individual and common good is essential for full professional participation in major issues in health care. Specific issues that challenge laboratory professionals in clinical research are allocation of health-care resources, testing conducted nearer the patient, confidentiality, screening tests, and molecular biology. A voice in ethical issues is an essential element of professional independence. The ethical attitudes we display influence the kind of people who choose to work in our profession. More open discussion about ethics is necessary in our professional literature.

The significance of matrix effects on the measurement of lactate dehydrogenase (LD) activity using Kodak dry slide technology in the Ontario Laboratory Proficiency Testing Program

A recent lactate dehydrogenase (LD) survey of the Laboratory Proficiency Testing Program (LPTP) of Ontario showed interlaboratory coefficients of variation ranging from 6.5% to 40% for five lyophilized vials on the 12 Kodak analyzers. All the LPTP survey samples had similar protein and LD isoenzyme electrophoretic patterns which remained unchanged after reconstitution and storage for 5 days at 4 degrees C, although the total LD activities fell. Four Ektachem 700 analyzers were subsequently tested using LPTP material and no difference in LD activity between instruments or between two LD slide lot numbers was shown. Generation 9 slides gave higher LD activities than generation 10 on all the reconstituted lyophilized proficiency testing samples. There was no significant difference between slide generations when 19 liquid human sera were analyzed, indicating that the variability on LPTP samples was due to a matrix effect. Definition of the matrix effect of lyophilized proficiency testing material is essential before any proficiency testing program can use such material to reflect analytical performance on patient specimens.

Assessment of the accuracy of serial electrocardiograms in the diagnosis of myocardial infarction

The diagnostic accuracy of the 12-lead scalar electrocardiogram (ECG) for the presence or absence of acute transmural myocardium infarction (MI) was studied in 25 patients who died while in hospital for treatment of ischemic chest pain. Detailed autopsy studies revealed myocardial necrosis in 17 patients, with the ECG accurate in 11 (44%) of the 25 patients. None of the five patients with autopsy-proven subendocardial infarction had abnormal Q waves. The admission ECG was diagnostic in only 4 of the 17 patients (24%) with infarction. The creatine kinase (CK) and CK-MB results agreed with the pathologic findings in 22 of the 25 patients (88%), were falsely negative in one patient, and falsely positive in two of the patients. In this selected population the most reliable diagnostic tests were CK or CK-MB isoenzymes. The ECG was frequently unhelpful (7 of 25 patients) because of left bundle branch block or paced rhythm, but when unaffected by these depolarization abnormalities it was useful in establishing the correct diagnosis.

Detection of ischemic myocardial injury in patients with normal, or moderately elevated, serum CK and AST activities

It is still undecided in clinical medicine if an increased serum CK-MB level indicates irreversible myocardial damage. We measured CK and AST activities on three serum samples obtained during the first 24 hours following admission of patients with a clinical history suggesting myocardial ischemia. Isoenzymes were not separated when CK and AST activities were less than 300 U/L and 35 U/L respectively, but were fractionated when the enzyme activities doubled during the first 24 hours even within their normal ranges. Over a three-year period this doubling occurred in 30 patients, one of whom was admitted twice to the hospital. The serum CK-MB fractions of these patients were 6% or greater in 26 and less than 6% in 5 admissions. The final clinical diagnosis given to the patients on 20 of these 26 admissions was acute subendocardial infarction. None of the five patients with a CK-MB fraction less than 6% had a clinical diagnosis of acute myocardial infarction. A comparative study of 102 patients with higher average enzyme activities but without doubling of both enzymes during a 24-hour period, did not yield a CK-MB of 6% or greater. None of this group of patients was diagnosed clinically as having had acute myocardial infarction.