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Comparison between Methylation-specific Multiplex Ligation-dependent Probe Amplification and Methylation-specific PCR in Diagnosis of Prader-Willi Syndrome
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摘要:
目的 应用甲基化特异性PCR(methylation-specific PCR, MS-PCR)和甲基化特异性多重连接探针扩增(methylation-specific multiplex ligation-dependent probe amplification, MS-MLPA)方法对Prader-Willi综合征(Prader-Willi syndrome, PWS)进行诊断并比较两种方法的差异。 方法 回顾性研究2005年10月至2014年2月到北京协和医院就诊的患儿及正常对照共102例, 男57例, 女45例。其中正常对照16例; 荧光原位杂交或高分辨染色体确诊PWS阳性对照2例; 临床疑似PWS患儿84例。提取受试者外周血基因组DNA分别应用MS-PCR及MS-MLPA方法进行基因分析, 对疑似患儿进行确诊和遗传类型分型, 并计算两种方法的特异性、敏感性及准确度, 应用卡方检验对两种方法进行比较。 结果 MS-PCR结果示正常对照及阳性对照与其表型全部相符, 84例疑似患儿中有39例提示为PWS, 45例提示正常。MS-MLPA结果示除正常对照外的86例受试者中, 29例提示为父源缺失型PWS; 9例提示为母源二体型PWS; 47例提示为正常; 1例因DNA过于陈旧未检出有效结果。对比两种方法检测结果, 有2例MS-PCR结果显示为PWS, 但MS-MLPA结果显示为正常, 通过增加DNA用量重新进行MS-PCR检测后, 除外PWS。结合临床表现, 受试者中明确诊断PWS的患儿39例, 非PWS者63例。MS-PCR方法共出现2例假阳性, 假阳性率为3.17%(2/63)。MS-PCR方法敏感性100%, 特异性96.83%, 准确度98.03%;MS-MLPA方法敏感性97.43%, 特异性100%, 准确度99.02%。两种方法的敏感性、特异性及准确度差异无统计学意义(P均 > 0.05)。 结论 MS-PCR及MS-MLPA敏感性、特异性及准确度皆佳, 均可用于PWS诊断, MS-MLPA可区分父源缺失型及母源二体型。MS-PCR应保证DNA用量充足以避免假阳性出现。MS-MLPA应使用新鲜提取的DNA, 且实验条件要求更为严格。建议同时使用两种方法检测以获得准确结果。 -
关键词:
- Prader-Will综合征 /
- 甲基化特异性PCR /
- 甲基化特异性多重连接探针扩增
Abstract:Objective To compare the diagnostic effectiveness of methylation-specific PCR (MS-PCR) and methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) in clinical suspected Prader-Willi syndrome (PWS). Methods One hundred and two participants (57 males and 45 females) who visited Peking Union Medical College Hospital in the period from October 2005 to February 2014 were included inthis retrospective study. Among the 102 participants, 16 were normal controls, 2 PWS cases confirmed by fluorescence in situ hybridization or high resolutin banding were positive controls, and 84 were suspected PWS cases. Genomic DNA was extracted for MS-PCR and MS-MLPA, based on which diagnoses were made and genetic types distinguished. Chi-squared test was used to compare the sensitivity, specificity, and accuracy of the two methods. Results MS-PCR results showed that all normal controls and positive controls were conform to their phenotypes. Thirty-nine in the 84 suspected patients were shown to be PWS, and the other 45 to be normal. MS-MLPA showed that in the 86 non-normal participants (positive control and suspected cases), 29 had paternal deletions, 9 had maternal uniparental disomy (mUPD), 47 were normal; and the assay failed to produce effective result in 1 case due to the overlong DNA storage time. Two participants were diagnosed as PWS cases by MS-PCR but normal by MS-MLPA. The diagnosis of PWS was ruled out by repeat MS-PCR after doubling DNA dosage. Combined with clinical manifestations, 39 participants were definitively diagnosed as PWS, the other 63 were not PWS. The false-positive rate of MS-PCR was 3.17%(2/63).The sensitivity, specificity, and accuracy of MS-PCR were 100%, 96.83%, and 98.03%, respectively; while those indicators of MS-MLPA were 97.43%, 100%, and 99.02%, respectively, showing no significant difference (all P > 0.05). Conclusions Both MS-PCR and MS-MLPA have high sensitivity, specificity, and accuracy, thus are effective for PWS diagnosis. MS-MLPA can distinguish paternal deletion and mUPD. Enough dose of DNA is requisite in MS-PCR to avoid false-positive results. Freshness of DNA samples is essential in MS-MLPA, which also needs more strict performance standards. We suggest a combination of MS-PCR and MS-MLPA in diagnosing PWS to ensure the accuracy of the result. -
图 1 MS-PCR检测结果
N:疑似患儿中提示为非PWS；PWS:疑似患儿中提示为PWS；PWSC：临床确诊的PWS阳性对照；SC：系统对照；NC：正常对照；MS-PCR：甲基化特异性PCR；PWS：Prader-Willi综合征
图 2 受试者MS-MLPA分析结果
A.男性正常对照；B.疑似患儿中提示为非PWS的男性患儿；C.疑似患儿中提示为父源缺失型PWS的女性患儿；D.疑似患儿中提示为父源缺失型PWS的男性患儿；E.疑似患儿中被诊断为母源同源二体型PWS的女性患儿MS-MLPA：甲基化特异性多重连接探针扩增；PWS：同图 1
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