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Are our HDL assays fit for purpose?
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Abstracts / Atherosclerosis 213 (2010) e1–e5
Are our HDL assays fit for purpose? Marrington ∗ ,
Craig Webster, Pamela Rachel Macerola, Christina Jewkes, Alan Jones
Sturges, Eileen
Department of Clinical Biochemistry and Immunology, Birmingham Heartlands Hospital, Heart of England NHS Foundation Trust, Birmingham, United Kingdom High density lipoprotein cholesterol (HDL-C) is routinely measured to assess patients’ risks of cardiovascular disease and to calculate low density lipoprotein cholesterol (LDL-C) concentrations. The reference method for HDL-C is ultracentrifugation, but is too laborious for routine clinical measurements. Precipitation of apolipoprotein B lipoproteins with measurement of HDL-C in the supernatant correlates well with ultracentrifugation, and this assay underpins many landmark studies. This technique is also time consuming and has been succeeded by ‘direct’ HDL-C methods which obviate precipitation. Recently we noted an unexpected number of very high HDL-C values. We therefore analysed patient mean HDL-C values over the last decade across our two laboratories, which showed a gradual increase from 1.12 to an implausible value of 1.56 mmol/L; the percentage of HDL-C values >2 mmol/L increased from 3.4 to 11.0%, peaking at 15.9%. Over this period our internal/external quality assurance (QA) performance was satisfactory, and indeed we had a negative bias to the all laboratories true mean (ALTM). Hence we compared HDL-C measured by our routine ‘third generation’ direct method (Roche) and by phosphotungstate precipitation (Randox). The ‘direct’ method had a proportional positive bias of 0.1 at low, to 1.3 mmol/L at high HDL-C concentrations. We speculate that this phenomenon is not unique to our laboratory but may apply to others using ‘direct’ HDL assays. We suggest that reliance on the ALTM for QA and the absence of a primary reference standard is inappropriate for HDL-C. Over-estimation of HDL-C will have a significant impact on risk assessment and LDL calculations. doi:10.1016/j.atherosclerosis.2010.07.033 Familial hyperlipidaemia in Scotland 2010: Report from the Scottish lipid forum W.G. Simpson 1,∗ , Z. Miedzybrodzka 2 , R. Finnie 1,3 , H. Gregory 4 , J. Series 5 , M. Van Mourik 6 , on behalf of the Scottish Lipid Forum 1
Clinical Biochemistry, Aberdeen Royal Infirmary, Aberdeen, United Kingdom 2 Medical Genetics, Aberdeen Royal Infirmary, Aberdeen, United Kingdom 3 Dedridge Health Centre and St John’s Hospital, Livingston, United Kingdom 4 Rosemount Medical Group, Aberdeen, United Kingdom 5 Clinical Biochemistry, Vale of Leven Hospital, Alexandria, United Kingdom 6 Ferguson-Smith Centre for Clinical Genetics, Glasgow, United Kingdom Following publication of the NICE Guideline on Identification and management of familial hypercholesterolaemia (FH) in 2008, the Scottish Lipid Forum met in November 2008 with representation from the Scottish Genetics Consortium to map a pathway for implementation of the guideline in Scotland (estimated prevalence of FH approx 10,000). Standard procedures were agreed and adopted, facilitating genetic testing for FH in Scotland. It was decided at the outset that a full sequence analysis would be performed as the frequency of
known single nucleotide polymorphisms (SNPs) had not yet been determined in the Scottish population. Initially the test was made available through Lipid Clinics, who were already reviewing many individuals with definite or possible FH as categorized by the Simon Broome criteria. A review meeting was arranged in November 2009 to refine the referral process and agree a process for cascading genetic testing where appropriate. To date, 350 individuals have been tested for genetic alterations leading to FH, and 122 changes have been found (detection rate 35%). 112 of these were in the LDL receptor gene (LDLR), including 95 SNPs and 17 with duplications/deletions. 5 specific SNPs were relatively common, but in total 52 different SNPs in the LDLR have been found in this population to date. A further 10 individuals have changes in the Apolipoprotein B gene (APOB), 9 of these being the common SNP. No alterations of the PCSK9 gene have been found in this population. Conclusion – it remains necessary to undertake the full LDLR sequence analysis in Scotland. doi:10.1016/j.atherosclerosis.2010.07.034 Lipoprotein associations with endothelial dysfunction and carotid intima-media thickness in young people with Type 1 diabetes Latika Sibal 1,∗ , Dermot Neely 2 , Anne Jones 3 , George Mitchell 4 , Crispian Oates 4 , Philip D. Home 1,3 1 Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom 2 Biochemistry Department, Newcastle upon Tyne Hospitals, Newcastle upon Tyne, United Kingdom 3 Newcastle Diabetes Centre, Newcastle upon Tyne Hospitals, Newcastle upon Tyne, United Kingdom 4 Regional Medical Physics Department, Newcastle upon Tyne Hospitals, Newcastle upon Tyne, United Kingdom
Aims: Endothelial dysfunction, carotid intima-media thickness (CIMT), and lipoprotein abnormalities predate cardiovascular disease (CVD). Non-HDL-C has been found to be more strongly correlated to apolipoprotein B than LDL-C in people with Type 1 diabetes (T1DM). We studied the associations between lipoprotein measures estimated by the routine assay and the designated reference method with endothelial function and CIMT in young people with Type 1 diabetes without microalbuminuria or extant arterial disease. Methods: Flow-mediated dilation (FMD), CIMT, and lipoproteins were examined in 154 young people, 74 with T1DM and 80 healthy controls. FMD and CIMT were assessed using ultrasonography. Fasting and postprandial lipids were measured, with LDL-C calculated by the Friedewald equation but also measured by beta-quantification (BQ) in the fasting state. Apolipoproteins A1 and B100, and oxidised LDL-C were also measured. Results: CIMT was associated with non-HDL-C (r = 0.30, p = 0.012), remaining significant after adjustment for age and sex. CIMT was positively correlated with both Friedewald- and BQLDL-C (r = 0.27 for both assays, p = 0.020–0.024). Although the association between apolipoprotein B and CIMT did not reach statistical significance on univariate analysis (r = 0.23, p = 0.059), this was significant after adjusting for age and sex (p = 0.032). No statistically significant association was found between FMD and non-HDL-C (r = −0.11, p = 0.372). Reduced FMD was associated with lower apolipoprotein A1 (r = 0.42, p < 0.001), and lower serum HDL-C measured by either method (routine r = 0.39, p = 0.001 fasting and r = 0.34, p = 0.005 postprandially; BQ-HDL-C r = 0.34, p = 0.003).
Abstracts / Atherosclerosis 213 (2010) e1–e5
Are our HDL assays fit for purpose? Marrington ∗ ,
Craig Webster, Pamela Rachel Macerola, Christina Jewkes, Alan Jones
Sturges, Eileen
Department of Clinical Biochemistry and Immunology, Birmingham Heartlands Hospital, Heart of England NHS Foundation Trust, Birmingham, United Kingdom High density lipoprotein cholesterol (HDL-C) is routinely measured to assess patients’ risks of cardiovascular disease and to calculate low density lipoprotein cholesterol (LDL-C) concentrations. The reference method for HDL-C is ultracentrifugation, but is too laborious for routine clinical measurements. Precipitation of apolipoprotein B lipoproteins with measurement of HDL-C in the supernatant correlates well with ultracentrifugation, and this assay underpins many landmark studies. This technique is also time consuming and has been succeeded by ‘direct’ HDL-C methods which obviate precipitation. Recently we noted an unexpected number of very high HDL-C values. We therefore analysed patient mean HDL-C values over the last decade across our two laboratories, which showed a gradual increase from 1.12 to an implausible value of 1.56 mmol/L; the percentage of HDL-C values >2 mmol/L increased from 3.4 to 11.0%, peaking at 15.9%. Over this period our internal/external quality assurance (QA) performance was satisfactory, and indeed we had a negative bias to the all laboratories true mean (ALTM). Hence we compared HDL-C measured by our routine ‘third generation’ direct method (Roche) and by phosphotungstate precipitation (Randox). The ‘direct’ method had a proportional positive bias of 0.1 at low, to 1.3 mmol/L at high HDL-C concentrations. We speculate that this phenomenon is not unique to our laboratory but may apply to others using ‘direct’ HDL assays. We suggest that reliance on the ALTM for QA and the absence of a primary reference standard is inappropriate for HDL-C. Over-estimation of HDL-C will have a significant impact on risk assessment and LDL calculations. doi:10.1016/j.atherosclerosis.2010.07.033 Familial hyperlipidaemia in Scotland 2010: Report from the Scottish lipid forum W.G. Simpson 1,∗ , Z. Miedzybrodzka 2 , R. Finnie 1,3 , H. Gregory 4 , J. Series 5 , M. Van Mourik 6 , on behalf of the Scottish Lipid Forum 1
Clinical Biochemistry, Aberdeen Royal Infirmary, Aberdeen, United Kingdom 2 Medical Genetics, Aberdeen Royal Infirmary, Aberdeen, United Kingdom 3 Dedridge Health Centre and St John’s Hospital, Livingston, United Kingdom 4 Rosemount Medical Group, Aberdeen, United Kingdom 5 Clinical Biochemistry, Vale of Leven Hospital, Alexandria, United Kingdom 6 Ferguson-Smith Centre for Clinical Genetics, Glasgow, United Kingdom Following publication of the NICE Guideline on Identification and management of familial hypercholesterolaemia (FH) in 2008, the Scottish Lipid Forum met in November 2008 with representation from the Scottish Genetics Consortium to map a pathway for implementation of the guideline in Scotland (estimated prevalence of FH approx 10,000). Standard procedures were agreed and adopted, facilitating genetic testing for FH in Scotland. It was decided at the outset that a full sequence analysis would be performed as the frequency of
known single nucleotide polymorphisms (SNPs) had not yet been determined in the Scottish population. Initially the test was made available through Lipid Clinics, who were already reviewing many individuals with definite or possible FH as categorized by the Simon Broome criteria. A review meeting was arranged in November 2009 to refine the referral process and agree a process for cascading genetic testing where appropriate. To date, 350 individuals have been tested for genetic alterations leading to FH, and 122 changes have been found (detection rate 35%). 112 of these were in the LDL receptor gene (LDLR), including 95 SNPs and 17 with duplications/deletions. 5 specific SNPs were relatively common, but in total 52 different SNPs in the LDLR have been found in this population to date. A further 10 individuals have changes in the Apolipoprotein B gene (APOB), 9 of these being the common SNP. No alterations of the PCSK9 gene have been found in this population. Conclusion – it remains necessary to undertake the full LDLR sequence analysis in Scotland. doi:10.1016/j.atherosclerosis.2010.07.034 Lipoprotein associations with endothelial dysfunction and carotid intima-media thickness in young people with Type 1 diabetes Latika Sibal 1,∗ , Dermot Neely 2 , Anne Jones 3 , George Mitchell 4 , Crispian Oates 4 , Philip D. Home 1,3 1 Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom 2 Biochemistry Department, Newcastle upon Tyne Hospitals, Newcastle upon Tyne, United Kingdom 3 Newcastle Diabetes Centre, Newcastle upon Tyne Hospitals, Newcastle upon Tyne, United Kingdom 4 Regional Medical Physics Department, Newcastle upon Tyne Hospitals, Newcastle upon Tyne, United Kingdom
Aims: Endothelial dysfunction, carotid intima-media thickness (CIMT), and lipoprotein abnormalities predate cardiovascular disease (CVD). Non-HDL-C has been found to be more strongly correlated to apolipoprotein B than LDL-C in people with Type 1 diabetes (T1DM). We studied the associations between lipoprotein measures estimated by the routine assay and the designated reference method with endothelial function and CIMT in young people with Type 1 diabetes without microalbuminuria or extant arterial disease. Methods: Flow-mediated dilation (FMD), CIMT, and lipoproteins were examined in 154 young people, 74 with T1DM and 80 healthy controls. FMD and CIMT were assessed using ultrasonography. Fasting and postprandial lipids were measured, with LDL-C calculated by the Friedewald equation but also measured by beta-quantification (BQ) in the fasting state. Apolipoproteins A1 and B100, and oxidised LDL-C were also measured. Results: CIMT was associated with non-HDL-C (r = 0.30, p = 0.012), remaining significant after adjustment for age and sex. CIMT was positively correlated with both Friedewald- and BQLDL-C (r = 0.27 for both assays, p = 0.020–0.024). Although the association between apolipoprotein B and CIMT did not reach statistical significance on univariate analysis (r = 0.23, p = 0.059), this was significant after adjusting for age and sex (p = 0.032). No statistically significant association was found between FMD and non-HDL-C (r = −0.11, p = 0.372). Reduced FMD was associated with lower apolipoprotein A1 (r = 0.42, p < 0.001), and lower serum HDL-C measured by either method (routine r = 0.39, p = 0.001 fasting and r = 0.34, p = 0.005 postprandially; BQ-HDL-C r = 0.34, p = 0.003).