Background

The revised national guidelines for analysis of cerebrospinal fluid for bilirubin in suspected subarachnoid haemorrhage (UK) provide an objective means of assessing cerebrospinal fluid (CSF) samples to determine risk of subarachnoid haemorrhage (SAH). The guidelines are intended for general use, but samples rendered uninterpretable due to the presence of the antibiotic doxycycline have been described. Here, further cases of antibiotic- based interference, and their implications, are presented.

Methods

An archival search of CSF spectra performed at Hallands County Hospital Halmstad was performed for the years 2011 and 2016- 2019 in an attempt to locate instances of interference. Each case of suspected interference was further investigated with in vitro reproduction experiments as a means of confirmation and assessment of potential clinical impact.

Results

A total of 10 cases of CSF curve interference were discovered: 6 due to doxycycline, 3 due to metronidazole and 1 due to tetracycline. Interference due to the tetracycline class was revealed through in vitro experimentation to cause an apparent decrease in the sample’s net bilirubin absorbance(NBA); the presence of xanthochromia on visual inspection was, however, conserved.

Conclusions

The problem of CSF absorbance curve interference might be more common than previously suspected. Due to the potential NBA- lowering effect of tetracyclines, the author recommends visual examination of CSF samples in every case.

 背景

修订后的疑似蛛网膜下腔出血脑脊液胆红素分析国家指南（英国）提供了评估脑脊液（CSF）样本以确定蛛网膜下腔出血（SAH）风险的客观方法。该指南旨在供一般用途，但由于抗生素强力霉素的存在而导致无法解释的样本已被描述。这里介绍了更多基于抗生素的干扰案例及其影响。

 方法

哈尔姆斯塔德哈兰县医院对 2011 年和 2016-2019 年的脑脊液频谱进行了档案检索，试图找到干扰实例。通过体外繁殖实验进一步研究每个可疑干扰的病例，作为确认和评估潜在临床影响的手段。

 结果

共发现脑脊液曲线干扰10例：强力霉素6例，甲硝唑3例，四环素1例。通过体外实验发现四环素类干扰导致样品净胆红素吸光度（NBA）明显下降；然而，目视检查时黄色素的存在是保留的。

 结论

脑脊液吸光度曲线干扰问题可能比之前怀疑的更为常见。由于四环素类药物具有潜在的降低 NBA 的作用，作者建议对每种情况下的脑脊液样本进行目视检查。