Endocrine Abstracts

Background: 5-hydroxyindole acetic acid (5-HIAA), a metabolite of serotonin, is used as a marker for patients with serotonin-secreting neuroendocrine tumours (NET). Currently, the majority of laboratories measure 5-HIAA excretion in 24 h urine samples. Given the practicality and analytic problems of these samples, our laboratory successfully developed a LC–MS/MS method for the analysis of 5-HIAA in serum samples. Further to this, we have now developed a method to measure 5-HIAA in whole blood samples.

Methods: We developed a method for measurement of 5-HIAA in whole blood samples using a simple protein precipitation step prior to LC–MS/MS analysis. To validate the method, ion suppression, recovery from spiked whole blood, linearity, inter- and intra-assay imprecision and lower limit of quantitation (LLOQ) was assessed. The analysis was performed in positive ion mode using a Waters Quattro Premier; the ion transitions were m/z 192.9>145.9 and 199.1>149.8 for 5-HIAA and d5-5-HIAA respectively.

Results: Using post-column infusion of 5-HIAA, ion suppression was deemed to be negligible. Mean recovery was 93% (range 85–101%), and the method was linear up to 100 000 nmol/l. Within batch and between batch imprecision (CV), assessed over the normal and pathological range, was <9.1 and <7% respectively. LLOQ was 12.5 nmol/l.

Conclusion: We have successfully developed and validated a method for the measurement of 5-HIAA in whole blood samples. It is proposed that this method could be further developed to enable measurement of 5-HIAA in fingerprick or dried blood samples.