Previously undiagnosed serotonin toxicity: From pre-anaesthetic assessment to postoperative management - a case report.

Background

Diagnosis of hyperparathyroidism requires measurement of parathyroid hormone (PTH) in the context of the plasma calcium and other factors, such as vitamin D status and renal function. Accurate classification depends upon an appropriate population reference interval. We examined local population plasma PTH reference intervals at four different UK sites using a common platform.

Methods

Plasma PTH results were extracted from laboratory information systems at four different UK sites, all using the Abbott Architect i2000 method. We included only people with normal adjusted serum calcium, magnesium, vitamin D, and renal function. Following outlier rejection lower and upper reference limits were derived.

Results

An overall reference interval for plasma PTH of 3.0-13.7 pmol/L was observed using a non-parametric approach compared to 2.9-14.1 pmol/L using a parametric approach, notably higher than the manufacturer's representative range of 1.6-7.2 pmol/L. We also noted statistically significant differences (p < 0.00001) between some sites with upper limits ranging from 11.5 to 15.8 pmol/L which may be due to different population characteristics of each group.

Conclusion

Locally derived reference intervals may be beneficial for UK populations and revised upper thresholds are necessary when using the Abbott PTH method to avoid inappropriate classification of patients as having hyperparathyroidism.