Introduction

Diagnosing lactose malabsorption is usually based on hydrogen excretion in breath after a lactose challenge. However, a proportion of subjects with lactose malabsorption will not present a rise in hydrogen. Measuring excretion of methane or stable isotope labeled ¹³CO₂ after ingestion of ¹³C-lactose has been proposed to mitigate this problem.

Objective

The aim of the study was to assess the performance of measuring methane and ¹³CO₂ in individuals with normal hydrogen excretion compared to a genetic lactase non-persistence test.

Methods

Individuals referred for lactose breath testing and healthy controls were included. Participants received ¹³C-enriched lactose, performed breath testing, and underwent genotyping for a marker of lactase non-persistence (13910C*T). Using genotype as gold standard, the performance of measuring methane and ¹³CO₂ excretion was assessed.

Results

151 subjects participated in the study, 50 of which presented a lactase non-persistent genotype. Of these, 72% were correctly diagnosed through hydrogen excretion of ≥ 20 ppm above baseline. In subjects with normal hydrogen excretion, cumulative ¹³C excretion had an area under the curve (AUC) of the receiver operating characteristics (ROC) curve of 0.852. Sensitivity was 93% and specificity was 51% for the current cutoff of 14.5%. The optimal cutoff was 12.65% (sensitivity 93%, specificity 70%). The ROC curve of peak methane had an AUC of 0.542 (sensitivity of 14%, specificity of 91% for cutoff ≥ 10 ppm).

Conclusions

In individuals with genetically demonstrated lactase non-persistence and negative hydrogen breath test, the use of ¹³C-lactose with measurement of ¹³CO₂ excretion and hydrogen is a well-performing test to detect the lactose malabsorption and performs better than methane in our cohort.

中文翻译：

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H2 阴性受试者呼吸测试中 13C 分析对诊断乳糖吸收不良的附加价值：概念研究验证

介绍

诊断乳糖吸收不良通常基于乳糖激发后呼吸中的氢气排泄。然而，一部分患有乳糖吸收不良的受试者不会出现氢含量升高的情况。已经提出测量摄入¹³ C-乳糖后甲烷或标记为¹³ CO _{2的稳定同位素的排泄来缓解这个问题。}

客观的

该研究的目的是评估与遗传乳糖酶非持久性测试相比，氢排泄正常的个体测量甲烷和¹³ CO _{2的性能。}

方法

包括转诊进行乳糖呼气测试的个人和健康对照者。参与者接受了富含¹³ C 的乳糖，进行了呼气测试，并接受了乳糖酶非持久性标志物 (13910C*T) 的基因分型。使用基因型作为金标准，评估了测量甲烷和¹³ CO ₂排泄的性能。

结果

151 名受试者参与了这项研究，其中 50 名受试者呈现乳糖酶非持久性基因型。其中，72% 的患者通过氢排泄量高于基线 ≥ 20 ppm 得到正确诊断。在氢气排泄正常的受试者中，累积¹³ C 排泄的受试者工作特征 (ROC) 曲线下面积 (AUC) 为 0.852。对于 14.5% 的当前截止值，灵敏度为 93%，特异性为 51%。最佳截止值为 12.65%（敏感性 93%，特异性 70%）。峰值甲烷的 ROC 曲线的 AUC 为 0.542（截止值 ≥ 10 ppm 的灵敏度为 14%，特异性为 91%）。

结论

在基因证明乳糖酶不持久且氢气呼气测试呈阴性的个体中，使用¹³ C-乳糖测量¹³ CO ₂排泄和氢气是检测乳糖吸收不良的良好测试，并且在我们的队列中比甲烷表现更好。