A comparison of molecular and cytogenetic techniques for the diagnosis of pregnancy loss.

PURPOSE: To evaluate the sensitivity, specificity, advantages, and limitations of multiplex ligation-dependent probe amplification compared with conventional karyotype analysis in the investigation of contributing factors to recurrent pregnancy loss. METHOD: A cohort of 284 patients underwent side-by-side analysis of products of conception by both conventional karyotyping and multiplex ligation-dependent probe amplification with direct comparison of results. RESULTS: Multiplex ligation-dependent probe amplification was shown to enable a diagnosis for an additional 47 (16.5%) patients compared with conventional karyotype analysis. However, this advantage was offset by some disadvantages of the method, including a high false-positive rate (8/104; 7.7%), as demonstrated by single-arm probe abnormalities of uncertain clinical significance, as well as the inability to characterize structural rearrangements, such as Robertsonian translocations, which comprised 2.46% of samples (99% confidence interval = 0.09-4.83), and ploidy changes. The calculated performance characteristics of multiplex ligation-dependent probe amplification in this cohort yielded a sensitivity of 86.9% and specificity of 92.4%. CONCLUSIONS: The advantages of now widely accepted molecular methodologies, such as lower failure rates, faster turnaround times, and lower cost, must be complemented by adequate counseling, family follow-up, and specific diagnostic reporting practices. It is particularly important to specifically address the important limitations of the methodology, including the inability to characterize balanced structural rearrangements and ploidy changes, especially if multiplex ligation-dependent probe amplification is to be performed alone.

Measurement of the clinical utility of a combined mutation detection protocol in carriers of Duchenne and Becker muscular dystrophy.

BACKGROUND: Recent methodological advances have improved the detection rate for dystrophin mutations, but there are no published studies that have measured the clinical utility of these protocols for carrier detection compared with conventional carrier testing protocols that use pedigree, serum creatine kinase levels and linkage analysis. METHODS AND SUBJECTS: The clinical utility of a combined mutation detection protocol was measured. It involved quantitative PCR procedures followed by DNA sequence analysis for the identification of dystrophin mutation carriers in 2101 women at risk of being carriers from 348 mutation-known Duchenne or Becker muscular dystrophy pedigrees. RESULTS: The combined mutation detection protocol identified a mutation in 96% and 82% of index cases of Duchenne muscular dystrophy and Becker muscular dystrophy, respectively. An additional 692 (33%) potential carriers were correctly classified by the combined mutation detection protocol compared with pedigree, serum creatine kinase levels and linkage analysis. Significantly lower mutation carrier rates were identified in the mothers of isolated cases with deletion mutations than predicted from theoretical considerations, but these findings were not confirmed for duplication and DNA sequence mutations. CONCLUSIONS: There are significant clinical benefits to be gained from a combined mutation detection protocol for carrier detection. It is recommended that mutation-specific carrier frequencies for the different classes of dystrophin mutations should be taken into account in genetic counselling practice.