Silva M C, Coutinho P, Pinheiro C D, Neves J M, Serrano P
Department of Population Studies, Institute for Biomedical Sciences Abel Salazar, University of Porto, Portugal.
J Clin Epidemiol. 1997 Dec;50(12):1377-84. doi: 10.1016/s0895-4356(97)00202-3.
A project for studying the prevalence of hereditary ataxias (HA) and familial spastic paraplegias (FSP) in Portugal was set up in 1993. The ascertainment of patients in previous prevalence studies relied mainly on the information of hospital admissions and out-patient contacts with the neurology and other related departments at central hospitals covering the whole region surveyed. Many patients might be overlooked if large populations were studied using this method, since registers at central hospitals are very incomplete and for most part not yet computerized. On the other hand HA and FSP are rare diseases appearing in family clusters, and it would be unreasonable to undertake a sample survey based upon a suitable frame of the Portuguese population. Therefore we decided to carry out a two-phase prevalence survey at district level, involving the collaboration of all physicians working in the district health institutions and the population, in the screening of eligible subjects in phase 1. All subjects screened as positive were examined by a neurologist in phase 2. This method provided a direct estimate of false positives and false negatives were all patients also examined in phase 2, who came to our knowledge using other sources of information. The prevalence of hereditary ataxias and spastic paraplegias in the pilot district was 6.4 per 100,000 inhabitants. The sensitivity of the screening procedure was 81.2% and the predictive value of a positive screening was 25%. Considering the geographically circumscribed district nature of the populations to be studied, the comprehensive sources of case identification used and the high adherence of the health professionals involved, we believe that this method can be widely used, particularly in countries with similar health care services.
1993年，葡萄牙启动了一项研究遗传性共济失调（HA）和家族性痉挛性截瘫（FSP）患病率的项目。以往患病率研究中患者的确定主要依赖于医院入院信息以及与覆盖整个调查区域的中心医院神经科和其他相关科室的门诊接触情况。如果使用这种方法研究大量人群，许多患者可能会被遗漏，因为中心医院的登记非常不完整，而且大部分尚未计算机化。另一方面，HA和FSP是罕见病，呈家族聚集性出现，基于葡萄牙人口的合适框架进行抽样调查是不合理的。因此，我们决定在地区层面开展两阶段患病率调查，第一阶段筛查合格对象时，需要地区卫生机构的所有医生与民众合作。所有筛查为阳性的对象在第二阶段由神经科医生进行检查。这种方法直接估计了假阳性率，所有假阴性患者也在第二阶段进行了检查，这些患者是通过其他信息来源进入我们的视野的。试点地区遗传性共济失调和痉挛性截瘫的患病率为每10万居民6.4例。筛查程序的敏感性为81.2%，阳性筛查的预测值为25%。考虑到所研究人群的地理范围有限、病例识别的综合来源以及相关卫生专业人员的高依从性，我们认为这种方法可以广泛应用，特别是在具有类似医疗服务的国家。
