Five years of screening for galactosaemia in South Africa: Pitfalls of using Benedict’s test and thin layer chromatography to screen for galactosaemia in a developing country

Background The objective of the study was to investigate the effectiveness of screening for hereditary galactosaemia with Benedict’s test and thin layer chromatography (TLC) in a tertiary laboratory from a developing country. Methods We retrospectively analysed the results of tests done in suspected galactosaemia patients including Benedict’s test, thin layer chromatography, GALT activity and DNA analysis. Results 878 paediatric patients were screened with Benedict’s test; the age range was 5 days to 19 years. 48% tested positive/trace on the Benedict’s test of which 52% of these had galactosuria evident on TLC. 22% of this sample had pathologically low GALT results on follow-up. 8 patients from the screened population were confirmed to have galactosaemia, in addition to 6 more patients diagnosed with galactosaemia without screening tests performed. Median ages at which the diagnoses were made in the screened and non-screened samples were 2 months and 6 months respectively. Confirmatory DNA testing was performed in 2 patients, whom were found to be heterozygous for S135L mutation. Conclusion Inadequate performance of Benedict’s test and TLC was demonstrated by false positive and false negative results leading us to conclude that screening test results require interpretation with caution.

背景 本研究的目的是在一个发展中国家的三级实验室中，探究用班氏试验和薄层色谱法（TLC）筛查遗传性半乳糖血症的有效性。 方法 我们回顾性分析了疑似半乳糖血症患者的检测结果，包括班氏试验、薄层色谱法、半乳糖 -1 - 磷酸尿苷酰转移酶（GALT）活性以及DNA分析。 结果 878名儿科患者接受了班氏试验筛查；年龄范围为5天至19岁。48%的患者在班氏试验中呈阳性/弱阳性，其中52%在TLC上显示有半乳糖尿。在后续随访中，该样本中有22%的患者GALT结果呈病理性降低。在接受筛查的人群中，有8名患者被确诊为半乳糖血症，此外还有6名患者在未进行筛查试验的情况下被诊断为半乳糖血症。在接受筛查和未接受筛查的样本中，确诊的中位年龄分别为2个月和6个月。对2名患者进行了确诊性DNA检测，发现他们均为S135L突变杂合子。 结论 班氏试验和TLC因假阳性和假阴性结果而表现不佳，这使我们得出结论：对筛查试验结果的解读需谨慎。