Introduction. Familial hypercholesterolemia (FH) is an inherited disorder associated with a severely increased risk of cardiovascular disease. Although DNA test results in FH are associated with important medical and ethical consequences, data on accuracy of genetic tests is scarce. Methods. Therefore, we performed a prospective study to assess the overall accuracy of the DNA test used in the genetic cascade screening program for FH in The Netherlands. Individuals aged 18 years and older tested for one of the 5 most prevalent FH mutations, were included consecutively. DNA samples were analyzed by the reference and a counter-expertise laboratory following a standardized procedure. Results. 1003 cases were included. In the end, 317 (32%) carried an FH mutation, whereas in 686 (69%) samples no mutation was found. The overall accuracy of the reference laboratory was 99.8%, with two false positive results identified by the counter-expertise laboratory. Conclusion. The currently used mutation analysis is associated with a very low error rate. Therefore, we do not recommend routine use of duplicate testing. 1. Introduction The number of hereditary disorders for which a genetic test is available has increased from less than 200 in 1993 to more than 1,800 in 2009 [1]. Molecular genetic testing for these diseases raises a plethora of concerns, including the quality of test performance and interpretation of results [2]. Familial hypercholesterolemia (FH) is a condition that meets every criterion for genetic screening. FH is an autosomal codominant disorder of lipid metabolism with a prevalence of 1？:？500 in most Western countries [3]. Patients with FH have high plasma LDL cholesterol levels and an increased risk of coronary artery disease (CAD) [3, 4]. Statin therapy, intervening in the causal pathway of the disease, lowers CAD risk to a very significant extent in these individuals [5]. Defects in genes that code for proteins involved in hepatic clearance of low-density lipoprotein (LDL) cholesterol underlie the disorder [3]. In fact, more than a 1000 different mutations in the genes coding for the LDL-receptor (LDLR), apolipoprotein B (APOB), and proprotein convertase subtilisin/kexin type 9 (PCSK9) are known to cause FH [6]. Such a causal mutation can be identified by DNA analysis in a varying percentage of patients with a clinical FH diagnosis, ranging from 20% to more than 90%, with highest rates of detection in children strictly selected for severe clinical FH [7–13]. Knowledge of the causal monogenetic mutation enables rapid screening of family members for
References
[1]
A. L. Beaudet, “Which way for genetic-test regulation? Leave test interpretation to specialists,” Nature, vol. 466, no. 7308, pp. 816–817, 2010.
[2]
B. Chen, M. Gagnon, S. Shahangian, N. L. Anderson, D. A. Howerton, and D. Joe Boone, “Good laboratory practices for molecular genetic testing for heritable diseases and conditions,” Morbidity and Mortality Weekly Report, vol. 58, no. -6, pp. 1–29, 2009.
[3]
J. L. Goldstein, H. H. Hobbs, and M. S. Brown, The Metabolic and Molecular Bases of Inherited Disease, McGraw-Hill, New York, NY, USA, 2001.
[4]
R. Huijgen, M. N. Vissers, J. C. Defesche, P. J. Lansberg, J. J. P. Kastelein, and B. A. Hutten, “Familial hypercholesterolemia: current treatment and advances in management,” Expert Review of Cardiovascular Therapy, vol. 6, no. 4, pp. 567–581, 2008.
[5]
J. Versmissen, D. M. Oosterveer, M. Yazdanpanah et al., “Efficacy of statins in familial hypercholesterolaemia: a long term cohort study,” BMJ, vol. 337, p. a2423, 2008.
[6]
S. E. A. Leigh, A. H. Foster, R. A. Whittall, C. S. Hubbart, and S. E. Humphries, “Update and analysis of the university college London low density lipoprotein receptor familial hypercholesterolemia database,” Annals of Human Genetics, vol. 72, no. 4, pp. 485–498, 2008.
[7]
A. van der Graaf, H. J. Avis, D. M. Kusters et al., “Molecular basis of autosomal dominant hypercholesterolemia: assessment in a large cohort of hypercholesterolemic children,” Circulation, vol. 123, no. 11, pp. 1167–1173, 2011.
[8]
D. Damgaard, M. L. Larsen, P. H. Nissen et al., “The relationship of molecular genetic to clinical diagnosis of familial hypercholesterolemia in a Danish population,” Atherosclerosis, vol. 180, no. 1, pp. 155–160, 2005.
[9]
E. S. van Aalst-Cohen, A. C. M. Jansen, M. W. T. Tanck et al., “Diagnosing familial hypercholesterolaemia: the relevance of genetic testing,” European Heart Journal, vol. 27, no. 18, pp. 2240–2246, 2006.
[10]
L. Assouline, E. Levy, J. C. Feoli-Fonseca, C. Godbout, and M. Lambert, “Familial hypercholesterolemia: molecular, biochemical, and clinical characterization of a French-Canadian pediatric population,” Pediatrics, vol. 96, no. 2, pp. 239–246, 1995.
[11]
F. Campagna, F. Martino, M. Bifolco et al., “Detection of familial hypercholesterolemia in a cohort of children with hypercholesterolemia: results of a family and DNA-based screening,” Atherosclerosis, vol. 196, no. 1, pp. 356–364, 2008.
[12]
C. A. Graham, B. P. McIlhatton, C. W. Kirk et al., “Genetic screening protocol for familial hypercholesterolemia which includes splicing defects gives an improved mutation detection rate,” Atherosclerosis, vol. 182, no. 2, pp. 331–340, 2005.
[13]
F. E. R. Punzalan, R. G. Sy, R. S. Santos et al., “Low density lipoprotein-receptor (LDL-R) gene mutations among Filipinos with familial hypercholesterolemia,” Journal of Atherosclerosis and Thrombosis, vol. 12, no. 5, pp. 276–283, 2005.
[14]
M. A. W. Umans-Eckenhausen, J. C. Defesche, E. J. G. Sijbrands, R. L. J. M. Scheerder, and J. J. P. Kastelein, “Review of first 5 years of screening for familial hypercholesterolaemia in the Netherlands,” The Lancet, vol. 357, no. 9251, pp. 165–168, 2001.
[15]
R. Huijgen, I. Kindt, S. B. J. Verhoeven et al., “Two years after molecular diagnosis of familial hypercholesterolemia: majority on cholesterol-lowering treatment but a minority reaches treatment goal,” PLoS ONE, vol. 5, no. 2, Article ID e9220, 2010.
[16]
R. Huijgen, S. J. Homsma, B. A. Hutten et al., “Improved access to life insurance after genetic diagnosis of familial hypercholesterolaemia: cross-sectional postal questionnaire study,” European Journal of Human Genetics, vol. 20, no. 7, pp. 722–728, 2012.
[17]
S. J. M. Homsma, R. Huijgen, S. Middeldorp, E. J. G. Sijbrands, and J. J. P. Kastelein, “Molecular screening for familial hypercholesterolaemia: consequences for life and disability insurance,” European Journal of Human Genetics, vol. 16, no. 1, pp. 14–17, 2008.
[18]
R. Huijgen, I. Kindt, S. W. Fouchier et al., “Functionality of sequence variants in the genes coding for the low-density lipoprotein receptor and apolipoprotein B in individuals with inherited hypercholesterolemia,” Human Mutation, vol. 31, no. 6, pp. 752–760, 2010.
[19]
R. Huijgen, I. Kindt, J. C. Defesche, and J. J. Kastelein, “Cardiovascular risk in relation to functionality of sequence variants in the gene coding for the low-density lipoprotein receptor: a study among 29 365 individuals tested for 64 specific low-density lipoprotein-receptor sequence variants,” European Heart Journal, vol. 33, no. 18, pp. 2325–2330, 2012.
[20]
C. Cobbaert, G. J. M. Boerma, and J. Lindemans, “Evaluation of the Cholestech L.D.X. desktop analyser for cholesterol, HDL-cholesterol, and triacylglycerols in heparinized venous blood,” European Journal of Clinical Chemistry and Clinical Biochemistry, vol. 32, no. 5, pp. 391–394, 1994.
[21]
W. T. Friedewald, R. I. Levy, and D. S. Fredrickson, “Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge,” Clinical Chemistry, vol. 18, no. 6, pp. 499–502, 1972.
[22]
A. M. Gotto Jr., E. L. Bierman, and W. E. Connor, “Recommendations for treatment of hyperlipidemia in adults. A joint statement of the nutritism committee and the Council on arteriosclerosis,” Circulation, vol. 69, no. 5, 1984.
[23]
J. T. den Dunnen and S. E. Antonarakis, “Mutation nomenclature extensions and suggestions to describe complex mutations: a discussion,” Human Mutation, vol. 15, no. 1, pp. 7–12, 2000.
[24]
M. P. Lombardi, E. J. W. Redeker, J. C. Defesche et al., “Molecular genetic testing for familial hypercholesterolemia : spectrum of LDL receptor gene mutations in the Netherlands,” Clinical Genetics, vol. 57, no. 2, pp. 116–124, 2000.
[25]
S. W. Fouchier, J. J. P. Kastelein, and J. C. Defesche, “Update of the molecular basis of familial hypercholesterolemia in The Netherlands,” Human Mutation, vol. 26, no. 6, pp. 550–556, 2005.
[26]
S. Castillo, D. Tejedor, P. Mozas et al., “The apolipoprotein B R3500Q gene mutation in Spanish subjects with a clinical diagnosis of familial hypercholesterolemia,” Atherosclerosis, vol. 165, no. 1, pp. 127–135, 2002.
[27]
I. F. A. C. Fokkema, J. T. Den Dunnen, and P. E. M. Taschner, “LOVD: easy creation of a locus-specific sequence variation database using an “LSDB-in-a-Box” approach,” Human Mutation, vol. 26, no. 2, pp. 63–68, 2005.
[28]
D. M. Kusters, R. Huijgen, J. C. Defesche et al., “Founder mutations in the Netherlands: geographical distribution of the most prevalent mutations in the low-density lipoprotein receptor and apolipoprotein b genes,” Netherlands Heart Journal, vol. 19, no. 4, pp. 175–182, 2011.
[29]
R. Huijgen, A. D. M. Stork, J. C. Defesche et al., “Extreme xanthomatosis in patients with both familial hypercholesterolemia and cerebrotendinous xanthomatosis,” Clinical Genetics, vol. 81, no. 1, pp. 24–28, 2012.
[30]
P. J. Talmud, S. Shah, R. Whittall, et al., “Use of low-density lipoprotein cholesterol gene score to distinguish patients with polygenic and monogenic familial hypercholesterolaemia: a case-control study,” The Lancet, vol. 381, no. 9874, pp. 1293–1301, 2013.
