| Objective: To assess the diagnostic value of Polymerase chain reaction-Restriction fragment length polymorphism in children with spinal muscular atrophy and analyze the relation between telomeric portion of survival motor neuron gene expression and the types of SMA in terms of clinical.Methods: Twenty-three children with suspicion of spinal muscular atrophy in terms of clinical features were simultaneously diagnosed by gold standard and PCR-RFLP. The results from two methods were compared by the sensitivity, specificity, Kappa and probability.Result: Of totally 23 cases enrolled in this study, the 18 cases of SMA and 5 cases of non-SMA were diagnosed by the gold standard. However, the SMNt no deletion in 5 cases of non-SMA; the SMNt homologous deletion of 15 cases and no deletion of 8 cases in 18 cases of SMA was detected by PCR-RFLP, the total deletion rate of SMNt gene was 83.3%; the deletion rates of exon 7, 8 and both were respectively 72.2%, 77.8% and 66.7%. Compared with the gold standard, the sensitivity of PCR-RFLP was 83.3%, specificity was 100%, the positive predictive value was 100%, negative predictive value was 62.5%, validity was 86.96%, and the Kappa value was 0.685. The detection of SMNt gene deletion showed that the SMNt deletion of both exon 7 and 8 accounted for 88.9% in type I SMA, 66.7% in type II SMA, and 0 in type III SMA. On the contrary, the SMNt deletion rate of only exon 7 or 8 was highest in type III, and the deletion rate of exon 8 and both exon 7 and 8 in type I SMA was higher than type III SMA (P<0.05), but there were no significant differences in deletion rate of exon 7 among three types of SMA.Conclusion: PCR-RFLP was a simple, rapid and time-saving diagnostic method for SMA, and it was sensitive and specific, which was worth popularizing, especially for SMA I. The deletion of both exon 7 and 8 often means serious symptom and poor prognosis, whereas only exon 7 or 8 deletion often predicts light symptom and relatively good prognosis.
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