Mucopolysaccharidoses (MPS) are a family of lysosomal storage disorders which can lead to degenerative and irreversible skeletal, cardiovascular, pulmonary, and neurological damage. Current treatments, including hematopoietic stem cell transplantation and enzyme replacement therapy, have been found most effective if administered before clinical symptoms are present, highlighting the urgent need for the development of newborn screening.

This study analyzed 18,222 dried blood spot samples from newborns for both enzyme activity and glycosaminoglycan (GAG) concentration levels. GAG levels were measured using liquid chromatography tandem mass spectrometry. Results were compared to our previously established cutoff values for three subtypes of GAGs: dermatan sulfate (DS) and heparan sulfate (HS0S and HSNS). Samples that were high for two of the three GAGs were identified and screened a second time. Samples were also measured for iduronate-2-sulfatase and alfa-L-iduronidase activity.

A total of 300 samples were above the established cutoff values for at least two of the three GAGs after the first screening. One sample was determined through clinical and genetic testing to be a true positive for MPS II. The false positive rate after the first GAG screening was 1.64%. A Cochran's formula test showed that the samples available for the second screening were representative samples (p = .0000601). False positive rate after second GAG screening, extrapolated from the representative sample was 0.4%. False positive rate after enzyme activity assay by fluorimetry for IDUA and IDS enzymes was 0.21% and 0.18%. A combination of GAG and enzyme assays provided no false positive and false negative samples.

Two-tier screening involving a combination of enzyme activity and multiple GAGs should be considered the gold standard for the diagnosis of MPS patients.

粘多糖贮积酶（MPS）是溶酶体贮积病的一个家族，可导致骨骼变性，不可逆转，心血管，肺和神经系统损害。如果在出现临床症状之前给予治疗，包括造血干细胞移植和酶替代疗法在内的当前治疗方法最为有效，突显了新生儿筛查的迫切需要。

这项研究分析了18222例新生儿的干血斑样品的酶活性和糖胺聚糖（GAG）浓度水平。GAG水平使用液相色谱串联质谱法测量。将结果与我们先前确定的GAG三种亚型的临界值进行比较：硫酸皮肤素（DS）和硫酸乙酰肝素（HS0S和HSNS）。确定了三个GAG中两个中的高样品，并进行了第二次筛选。还测量了样品的异氰酸酯-2-硫酸酯酶和α-L-异戊糖苷酶活性。

首次筛选后，对于三个GAG中的至少两个，总共有300个样品高于设定的临界值。通过临床和基因测试确定一个样品为MPS II的真正阳性。第一次GAG筛查后的假阳性率为1.64％。Cochran公式测试表明，可用于第二次筛选的样品是代表性样品（p = .0000601）。从代表样品中推断出的第二次GAG筛选后的假阳性率为0.4％。通过荧光法测定酶活性后，IDUA和IDS酶的假阳性率分别为0.21％和0.18％。GAG和酶检测的组合没有提供假阳性和假阴性样品。

涉及酶活性和多种GAG的两级筛选应被视为诊断MPS患者的金标准。