Mutation detection rate and spectrum in familial hypercholesterolaemia patients in the UK pilot cascade project
Insights
Genetic testing for familial hypercholesterolaemia (FH) detects mutations more effectively in definite FH cases than possible FH cases. This study confirms the utility of ARMS kits but highlights the need for sequencing in comprehensive FH diagnostics.
Area of Science:
- Genetics
- Cardiovascular Disease
- Molecular Biology
Background:
- Cascade testing using DNA mutation information is now recommended in the UK for patients with familial hypercholesterolaemia (FH).
- Clinical diagnosis categorizes FH into definite (DFH) and possible (PFH) based on specific criteria.
Purpose of the Study:
- To compare the mutation detection rate and spectrum in FH patients with definite (DFH) versus possible (PFH) clinical diagnoses.
- To evaluate the effectiveness of different genetic testing methods, including ARMS, SSCP/dHPLC/sequencing, and MLPA, for identifying FH-causing mutations.
Main Methods:
- Six hundred and thirty-five FH probands from six UK centers were tested for 18 LDLR mutations, APOB p.Arg3527Gln, and PCSK9 p.Asp374Tyr using an ARMS kit.
- Samples without detected mutations underwent comprehensive screening including SSCP/dHPLC/direct-sequencing and MLPA for deletions/duplications in LDLR.
- Genetic data from 296 relatives across 100 families were analyzed.
Main Results:
- The mutation detection rate was significantly higher in DFH patients (56.3%) compared to PFH patients (28.4%).
- Overall, mutations were detected in 232 patients (36.5%), with 107 different mutations identified, including 6.9% not previously reported.
- The ARMS kit identified 44% of mutations, while MLPA detected 4.7%. Specific mutations like APOB p.Arg3527Gln (12%) and PCSK9 p.Asp374Tyr (1.7%) were also found.
- In tested relatives, 56.1% carried a mutation. Patients of Indian/Asian origin showed an acceptable detection rate (10 mutations in 31 individuals).
Conclusions:
- Mutation detection rates for FH are significantly higher in patients with definite clinical diagnoses compared to possible diagnoses.
- While ARMS kits are useful, comprehensive diagnostic services for FH require confirmatory sequencing.
- Genetic mutation testing demonstrates acceptable detection rates even in individuals with low clinical suspicion and those of Indian origin, supporting its broader application.
Abstract:
Cascade testing using DNA-mutation information is now recommended in the UK for patients with familial hypercholesterolaemia (FH). We compared the detection rate and mutation spectrum in FH patients with a clinical diagnosis of definite (DFH) and possible (PFH) FH. Six hundred and thirty-five probands from six UK centres were tested for 18 low-density lipoprotein receptor gene (LDLR) mutations, APOB p.Arg3527Gln and PCSK9 p.Asp374Tyr using a commercial amplification refractory mutation system (ARMS) kit. Samples with no mutation detected were screened in all exons by single strand conformation polymorphism analysis (SSCP)/denaturing high performance liquid chromatography electrophoresis (dHPLC)/direct-sequencing, followed by multiplex ligation-dependent probe amplification (MLPA) to detect deletions and duplications in LDLR.The detection rate was significantly higher in the 190 DFH patients compared to the 394 PFH patients (56.3% and 28.4%, p > 0.00001). Fifty-one patients had inadequate information to determine PFH/DFH status, and in this group the detection rate was similar to the PFH group (25.5%, p = 0.63 vs PFH). Overall, 232 patients had detected mutations (107 different; 6.9% not previously reported). The ARMS kit detected 100 (44%) and the MLPA kit 11 (4.7%). Twenty-eight (12%) of the patients had the APOB p.Arg3527Gln and four (1.7%) had the PCSK9 p.Asp374Tyr mutation. Of the 296 relatives tested from 100 families, a mutation was identified in 56.1%. In 31 patients of Indian/Asian origin 10 mutations (two previously unreported) were identified. The utility of the ARMS kit was confirmed, but sequencing is still required in a comprehensive diagnostic service for FH. Even in subjects with a low clinical suspicion of FH, and in those of Indian origin, mutation testing has an acceptable detection rate.
