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Impact of the lipidPLUS external proficiency testing program on the measurement of serum cholesterol, triglycerides and HDL cholesterol
39TH A N N U A L
CONFERENCE
OF THE CANADIAN
liver and significant cardiomegaly with myocardial muscle cell lipid accumulation. Skeletal muscle appeared normal. Organic acid analysis by GC/MS on post-mortcm urine showed a remarkable increase in saturated and unsaturated dicarboxyfic acids, most notably those in the range from C6 to C14 which suggested impaired beta-oxidation. ReU~spective analysis of acylcaruitines by tandem MS on blood spots obtained from the neonatal screening card showed elevated C14:1, C14"2, C16, C18:1 acylcaruitines, and were suggestive of very long chain scyl CoA dehydrogenase (VLCAD) deficiency. The pattern of metabolites appears most typical of VLCAD deficiency, but defmitive diagnosis awaits enzymic analysis. It is known that metabolism of very long chain fatty acids (VLCFA) largely occurs in the peroxisom~, however, this case confirms that mitochondria also have an important talc in VLCFA metabolism, since VLCAD is a membrane-bound mitochondrial enzyme. Inborn errors involving fatty acid oxidation should be considered in all infants with hypertrophic or dilated cardiomyopathy. In addition, these results serve to emphasize the diagnostic value of neonatal blood cards for confirmation and for neonatal screening.
AI and B and submit their results by Fax. Target values for the QC material are assigned using methods that axe re£erenoed and standardized to the accuracy base of the US CDC-sponsored Cholesterol Reference Method Laboratory Netwoda We are the Canadian representative to this network. To support this proficiency testing program we also offer technical support and secondary reference material to help laboratories improve their measurement. Objective To establish the efficacy of LIPIEFtn. Method We compared the analytical performance of a group of 47 labo. mtories at the beginning and end of a 2 year subscaiption (8 shipments). Results Using student's t-tests, we found flint there was improvement in the accuracy of the measurement of HDL cholesterol and trii0ycerides over the 2 year studies. There was no change in the accuracy of cholesterol analysis but results submitted both at the beginning and end of the evaluation were well within CSCC guidelines. Conclusions We conclude that the L I P ~ program is an effective adjunct to the standardization of lipid testing in Canada.
7 THE EFFECTS OF HMO-CoA REDUCTASE INHIBIT I O N O N C A R N I T I N E STATUS IN R A B B I T S Bhuivan J. and Seccombo D.W., Division of Clinical Chemistry, Department of Pathology and Laboratory Medicine, Vancouver Hospital and Health Sciences Centre, Vancouver BC V5Z IMg, Canada
Objectives ~ study exan~ed the effect of ~eatment with an HMG-C,oA reductsse inhibitor on serum and tissue levels of earuitine in the rabbit. Methods Rab~ta (n-6) were fed rabbit chow contaiuin8 iovastatin (30 ms/day) for 16 weeks. Blood was collected and tissues (liver, heart and skeletal muscle) harvested at sacrifice. Free and total camifinc were measured in serum and tissues by a radioenzymatic method. Camitine acetyitransferase (CAT) and earnitinc palmitoyitmnsferase (CPT) activities were determined and expressed relative to DNA. Results were compared to those obtained in chow-fed eontrois (n-6). Reaults Serum free (24.0+_.2.6 vs 29.4:1:3.1 ttM) and total (35.1+4.7 vs 52.8:1:8.8 pM) camitinc increased significantly after 16 weeks of treatmerit. This increase in serum total camitinc was mainly due to a significant increase in the acyl-caruitine fraction (12.7d:3.1 ,is 26.5+_.5.7 I ~ . Levels of total carnifine were siguificanfly decreased by U'estment in all tissues studied. The CAT activities in these tissues did not change significantly whereas the activities of CPT in liver and heart increased significantly with treatment. Conclusion Treatment with an HMG-CoA reductase alters the camitinc status in rabbits. 6
I M P A C T O F T H E L I P I D ~ m E X T E R N A L PROFI-
CIENCY TESTING PROGRAM ON THE MEASUREMENT OF SERUM CHOLESTEROL, TRIGLYCERIDES A N D H D L CHOLF~TEROL Hamilton. JJ_ Secmmbe, D.W., Ma(hhmess, C., Cribbs,P.R.,Klein, C. and Ped~ L., Cenadim Reference Labomt~y Limited,307-I083 Alma St., Vancouver, BC, Can!~, V6R 4N6
S O C I E T Y O F CLINICAL C H E M I S T S
EVALUATION OF DCL CREATINE KINASE-MB REAGENT ON THE C O B A S M I R A MacEachern. M.. Brown, J., and Murphy, D., Diagnostic Chemicals Limited, Chadottctown, PEI, CIE I]30, Canada
Laboratory testing of CK-MB can be diagnostically significant in the determination of myocardial infarction. The DCL CK-MB assay is a fast, simple, immuncehemical ~_s_~_yfor the direct determination of C K - M B isoenzymes in serum. Objectives 8. To evaluate the precision, linearity, and effect of interferents on the DCL CK-MB assay, b. To perform method comparisons to Sigma and Roche re~onts on the Cobas Mira, and a compmison to BMC produet on the I-Iitaehi704. Results Within-run precision studies on two sent gave precision estimates of 33.6:~0.6 U/L (I.8%CV) and 68.8.4:0.9 U/L (1A%CV). Lfnaarit), to 500 U/L and a lower limit of detection of 2 U/L were demonstinted. Interference studies showed that a hemoglobin level of 8 iunol/ L caused a positive interference of 10%. A bilirubin concentration of 250 pmol/L gave a positive interference of 14%, and an intndipid kvel of 5 mmol/L produced 10% positive interference. Method comparison results were as follows: Method
Instrument
n
slope
Intercept)
r
Sigma
Cobas Mira
40
0.95
1.4
0.99
BMC
Hitachi 704
40
0.89
13.3
0.98
Roche
Cpbas Mira
40
0.73
12.1
0.93
Conclusions We conclude that the DCL CK-MB Reagent is a refiable alternative for the determination of CK-MB in serum. DCL's sinsle-vial convenience and ease of use simplifies CK-MB testing to allow faster diagnosis of myocardial infarction.
In 1991 we created LIPIEPt~, a nationwide blind external proficiency testing program for lipids. On predetermined dates, perticipatingclinical laboratories are sent three freshly drawn human serum samples of differing lipid levels by overnight onorier. On receipt, lmflicipants measure total cholesterol, ~ 8 1 ~ HDL cholesterol and apolipopmtcins
324
CLINICAL BIOCHEMISTRY, VOLUME 28, J U N E 1995
CONFERENCE
OF THE CANADIAN
liver and significant cardiomegaly with myocardial muscle cell lipid accumulation. Skeletal muscle appeared normal. Organic acid analysis by GC/MS on post-mortcm urine showed a remarkable increase in saturated and unsaturated dicarboxyfic acids, most notably those in the range from C6 to C14 which suggested impaired beta-oxidation. ReU~spective analysis of acylcaruitines by tandem MS on blood spots obtained from the neonatal screening card showed elevated C14:1, C14"2, C16, C18:1 acylcaruitines, and were suggestive of very long chain scyl CoA dehydrogenase (VLCAD) deficiency. The pattern of metabolites appears most typical of VLCAD deficiency, but defmitive diagnosis awaits enzymic analysis. It is known that metabolism of very long chain fatty acids (VLCFA) largely occurs in the peroxisom~, however, this case confirms that mitochondria also have an important talc in VLCFA metabolism, since VLCAD is a membrane-bound mitochondrial enzyme. Inborn errors involving fatty acid oxidation should be considered in all infants with hypertrophic or dilated cardiomyopathy. In addition, these results serve to emphasize the diagnostic value of neonatal blood cards for confirmation and for neonatal screening.
AI and B and submit their results by Fax. Target values for the QC material are assigned using methods that axe re£erenoed and standardized to the accuracy base of the US CDC-sponsored Cholesterol Reference Method Laboratory Netwoda We are the Canadian representative to this network. To support this proficiency testing program we also offer technical support and secondary reference material to help laboratories improve their measurement. Objective To establish the efficacy of LIPIEFtn. Method We compared the analytical performance of a group of 47 labo. mtories at the beginning and end of a 2 year subscaiption (8 shipments). Results Using student's t-tests, we found flint there was improvement in the accuracy of the measurement of HDL cholesterol and trii0ycerides over the 2 year studies. There was no change in the accuracy of cholesterol analysis but results submitted both at the beginning and end of the evaluation were well within CSCC guidelines. Conclusions We conclude that the L I P ~ program is an effective adjunct to the standardization of lipid testing in Canada.
7 THE EFFECTS OF HMO-CoA REDUCTASE INHIBIT I O N O N C A R N I T I N E STATUS IN R A B B I T S Bhuivan J. and Seccombo D.W., Division of Clinical Chemistry, Department of Pathology and Laboratory Medicine, Vancouver Hospital and Health Sciences Centre, Vancouver BC V5Z IMg, Canada
Objectives ~ study exan~ed the effect of ~eatment with an HMG-C,oA reductsse inhibitor on serum and tissue levels of earuitine in the rabbit. Methods Rab~ta (n-6) were fed rabbit chow contaiuin8 iovastatin (30 ms/day) for 16 weeks. Blood was collected and tissues (liver, heart and skeletal muscle) harvested at sacrifice. Free and total camifinc were measured in serum and tissues by a radioenzymatic method. Camitine acetyitransferase (CAT) and earnitinc palmitoyitmnsferase (CPT) activities were determined and expressed relative to DNA. Results were compared to those obtained in chow-fed eontrois (n-6). Reaults Serum free (24.0+_.2.6 vs 29.4:1:3.1 ttM) and total (35.1+4.7 vs 52.8:1:8.8 pM) camitinc increased significantly after 16 weeks of treatmerit. This increase in serum total camitinc was mainly due to a significant increase in the acyl-caruitine fraction (12.7d:3.1 ,is 26.5+_.5.7 I ~ . Levels of total carnifine were siguificanfly decreased by U'estment in all tissues studied. The CAT activities in these tissues did not change significantly whereas the activities of CPT in liver and heart increased significantly with treatment. Conclusion Treatment with an HMG-CoA reductase alters the camitinc status in rabbits. 6
I M P A C T O F T H E L I P I D ~ m E X T E R N A L PROFI-
CIENCY TESTING PROGRAM ON THE MEASUREMENT OF SERUM CHOLESTEROL, TRIGLYCERIDES A N D H D L CHOLF~TEROL Hamilton. JJ_ Secmmbe, D.W., Ma(hhmess, C., Cribbs,P.R.,Klein, C. and Ped~ L., Cenadim Reference Labomt~y Limited,307-I083 Alma St., Vancouver, BC, Can!~, V6R 4N6
S O C I E T Y O F CLINICAL C H E M I S T S
EVALUATION OF DCL CREATINE KINASE-MB REAGENT ON THE C O B A S M I R A MacEachern. M.. Brown, J., and Murphy, D., Diagnostic Chemicals Limited, Chadottctown, PEI, CIE I]30, Canada
Laboratory testing of CK-MB can be diagnostically significant in the determination of myocardial infarction. The DCL CK-MB assay is a fast, simple, immuncehemical ~_s_~_yfor the direct determination of C K - M B isoenzymes in serum. Objectives 8. To evaluate the precision, linearity, and effect of interferents on the DCL CK-MB assay, b. To perform method comparisons to Sigma and Roche re~onts on the Cobas Mira, and a compmison to BMC produet on the I-Iitaehi704. Results Within-run precision studies on two sent gave precision estimates of 33.6:~0.6 U/L (I.8%CV) and 68.8.4:0.9 U/L (1A%CV). Lfnaarit), to 500 U/L and a lower limit of detection of 2 U/L were demonstinted. Interference studies showed that a hemoglobin level of 8 iunol/ L caused a positive interference of 10%. A bilirubin concentration of 250 pmol/L gave a positive interference of 14%, and an intndipid kvel of 5 mmol/L produced 10% positive interference. Method comparison results were as follows: Method
Instrument
n
slope
Intercept)
r
Sigma
Cobas Mira
40
0.95
1.4
0.99
BMC
Hitachi 704
40
0.89
13.3
0.98
Roche
Cpbas Mira
40
0.73
12.1
0.93
Conclusions We conclude that the DCL CK-MB Reagent is a refiable alternative for the determination of CK-MB in serum. DCL's sinsle-vial convenience and ease of use simplifies CK-MB testing to allow faster diagnosis of myocardial infarction.
In 1991 we created LIPIEPt~, a nationwide blind external proficiency testing program for lipids. On predetermined dates, perticipatingclinical laboratories are sent three freshly drawn human serum samples of differing lipid levels by overnight onorier. On receipt, lmflicipants measure total cholesterol, ~ 8 1 ~ HDL cholesterol and apolipopmtcins
324
CLINICAL BIOCHEMISTRY, VOLUME 28, J U N E 1995