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Pre-, post- or no acidification of urine samples for calcium analysis: does it matter?

  • Camille Chenevier-Gobeaux EMAIL logo , Marie Rogier , Imane Dridi-Brahimi , Eugénie Koumakis , Catherine Cormier and Didier Borderie
Published/Copyright: September 20, 2019
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Clinical Chemistry and Laboratory Medicine (CCLM)
From the journal Clinical Chemistry and Laboratory Medicine (CCLM) Volume 58 Issue 1

Abstract

Background

Measuring 24 h-urine calcium concentration is essential to evaluate calcium metabolism and excretion. Manufacturers recommend acidifying the urine before a measurement to ensure calcium solubility, but the literature offers controversial information on this pre-analytical treatment. The objectives of the study were (1) to compare pre-acidification (during urine collection) versus post-acidification (in the laboratory), and (2) to evaluate the impact of acidification on urinary calcium measurements in a large cohort.

Methods

We evaluated the effects of pre- and post-acidification on 24-h urine samples collected from 10 healthy volunteers. We further studied the impact of acidification on the calcium results for 567 urine samples from routine laboratory practice, including 46 hypercalciuria (≥7.5 mmol/24 h) samples.

Results

Calciuria values in healthy volunteers ranged from 0.6 to 12.5 mmol/24 h, and no statistical significance was found between non-acidified, pre-acidified and post-acidified conditions. A comparison of the values (ranging from 0.21 to 29.32 mmol/L) for 567 urine samples before and after acidification indicated 25 samples (4.4%) with analytical differences outside limits of acceptance. The bias observed for these deviant values ranged from −3.07 to 1.32 mmol/L; no patient was re-classified as hypercalciuric after acidification, and three patients with hypercalciuria were classified as normocalciuric after acidification. These three deviant patients represent 6.5% of hypercalciuric patients.

Conclusions

Our results indicate that pre- and post-acidification of urine is not necessary prior to routine calcium analysis.

Keywords: acidification; calcium; pre-analytical process; urine

  1. Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

  2. Research funding: None declared.

  3. Employment or leadership: None declared.

  4. Honorarium: None declared.

  5. Competing interests: The funding organization(s) played no role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the report for publication.

References

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Received: 2019-06-14
Accepted: 2019-08-28
Published Online: 2019-09-20
Published in Print: 2019-12-18

©2020 Walter de Gruyter GmbH, Berlin/Boston

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https://doi.org/10.1515/cclm-2019-0606
Keywords for this article
acidification; calcium; pre-analytical process; urine

Articles in the same Issue

  1. Frontmatter
  2. Editorial
  3. Reflex TSH strategy: the good, the bad and the ugly
  4. Review
  5. Shortcomings in the evaluation of biomarkers in ovarian cancer: a systematic review
  6. Mini Review
  7. Clinical application of presepsin as diagnostic biomarker of infection: overview and updates
  8. Opinion Paper
  9. Gut microbiotas and immune checkpoint inhibitor therapy response: a causal or coincidental relationship?
  10. EFLM Paper
  11. Systematic review and meta-analysis of within-subject and between-subject biological variation estimates of 20 haematological parameters
  12. General Clinical Chemistry and Laboratory Medicine
  13. Pre-, post- or no acidification of urine samples for calcium analysis: does it matter?
  14. Pre-analytical and analytical confounders of serum calprotectin as a biomarker in rheumatoid arthritis
  15. Dynamics of soluble syndecan-1 in maternal serum during and after pregnancies complicated by preeclampsia: a nested case control study
  16. Multi-site performance evaluation and Sigma metrics of 20 assays on the Atellica chemistry and immunoassay analyzers
  17. Plasma creatinine medians from patients partitioned by gender and age used as a tool for assessment of analytical stability at different concentrations
  18. Two-center comparison of 10 fully-automated commercial procalcitonin (PCT) immunoassays
  19. Method comparison of four clinically available assays for serum free light chain analysis
  20. Comparison of three different chemiluminescence assays and a rapid liquid chromatography tandem mass spectrometry method for measuring serum aldosterone
  21. Repeatability and reproducibility of lipoprotein particle profile measurements in plasma samples by ultracentrifugation
  22. Reference Values and Biological Variations
  23. A study on reference interval transference via linear regression
  24. Cancer Diagnostics
  25. Unstimulated high-sensitive thyroglobulin is a powerful prognostic predictor in patients with thyroid cancer
  26. Cardiovascular Diseases
  27. Analytical validation of a highly sensitive point-of-care system for cardiac troponin I determination
  28. Acknowledgment
  29. Letters to the Editor
  30. Are icteric and lipemic indices reliable to screen for hyperbilirubinemia and hypertriglyceridemia?
  31. Anti-streptavidin antibodies as a cause of false-positive results of streptavidin-based autoantibody assays
  32. Assessment of complement interference in anti-Müllerian hormone immunoassays
  33. Validating thyroid-stimulating hormone (TSH) reflexive testing cutpoints in a tertiary care institution
  34. Results of the second external quality assessment for human papillomavirus genotyping in Shanghai, China
  35. Development of suitable external quality control material for G6PD deficiency screening with the fluorescent spot test
  36. Non-linearity in commercially available lipase assays: still gaps to close
  37. JAK2, 46/1 haplotype and chronic myelogenous leukemia: diagnostic and therapeutic potential
  38. Congress Abstracts
  39. 11th National Scientifc Congress SPML
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