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

Camille Chenevier-Gobeaux 1 , 2 , Marie Rogier 3 , Imane Dridi-Brahimi 3 , Eugénie Koumakis 2 , Catherine Cormier 2  and Didier Borderie 3 , 4
  • 1 Service de Diagnostic Biologique Automatisé (SDBA), Hôpital Cochin, Hôpitaux Universitaires Paris Centre (HUPC), 27 rue du Faubourg Saint-Jacques, 75679 Paris cedex 14, France
  • 2 Service de Rhumatologie, Hôpital Cochin, Hôpitaux Universitaires Paris Centre (HUPC), Paris, France
  • 3 Service de Diagnostic Biologique Automatisé (SDBA), Hôpital Cochin, Hôpitaux Universitaires Paris Centre (HUPC), Paris cedex 14, France
  • 4 UMR 1124, Université Paris Descartes, Paris, France
Camille Chenevier-Gobeaux
  • Corresponding author
  • Service de Diagnostic Biologique Automatisé (SDBA), Hôpital Cochin, Hôpitaux Universitaires Paris Centre (HUPC), 27 rue du Faubourg Saint-Jacques, 75679 Paris cedex 14, France
  • Service de Rhumatologie, Hôpital Cochin, Hôpitaux Universitaires Paris Centre (HUPC), Paris, France
  • Email
  • Search for other articles:
  • degruyter.comGoogle Scholar
, Marie Rogier
  • Service de Diagnostic Biologique Automatisé (SDBA), Hôpital Cochin, Hôpitaux Universitaires Paris Centre (HUPC), Paris cedex 14, France
  • Search for other articles:
  • degruyter.comGoogle Scholar
, Imane Dridi-Brahimi
  • Service de Diagnostic Biologique Automatisé (SDBA), Hôpital Cochin, Hôpitaux Universitaires Paris Centre (HUPC), Paris cedex 14, France
  • Search for other articles:
  • degruyter.comGoogle Scholar
, Eugénie Koumakis
  • Service de Rhumatologie, Hôpital Cochin, Hôpitaux Universitaires Paris Centre (HUPC), Paris, France
  • Search for other articles:
  • degruyter.comGoogle Scholar
, Catherine Cormier
  • Service de Rhumatologie, Hôpital Cochin, Hôpitaux Universitaires Paris Centre (HUPC), Paris, France
  • Search for other articles:
  • degruyter.comGoogle Scholar
and Didier Borderie
  • Service de Diagnostic Biologique Automatisé (SDBA), Hôpital Cochin, Hôpitaux Universitaires Paris Centre (HUPC), Paris cedex 14, France
  • UMR 1124, Université Paris Descartes, Paris, France
  • Search for other articles:
  • degruyter.comGoogle Scholar

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.

  • 1.

    Gunn IR, Gaffney D. Clinical and laboratory features of calcium-sensing receptor disorders: a systematic review. Ann Clin Biochem 2004;41:441–58.

    • Crossref
    • PubMed
    • Export Citation
  • 2.

    Foley KF, Boccuzzi L. Urine calcium: laboratory measurement and clinical utility. Lab Med 2010;41:683–6.

    • Crossref
    • Export Citation
  • 3.

    Sodi R, Godber IM. Effect of refrigeration, centrifugation, acidification, heat treatment and storage on urine calcium, magnesium and phosphate. Clin Chem Lab Med 2016;54:e379–81.

    • PubMed
    • Export Citation
  • 4.

    Darn SM, Sodi R, Ranganath LR, Roberts NB, Duffield JR. Experimental and computer modelling speciation studies of the effect of pH and phosphate on the precipitation of calcium and magnesium salts in urine. Clin Chem Lab Med 2006;44:185–91.

    • PubMed
    • Export Citation
  • 5.

    Sodi R, Bailey LB, Glaysher J, Allars L, Roberts NB, Marks EM, et al. Acidification and urine calcium: is it a preanalytical necessity? Ann Clin Biochem 2009;46:484–7.

    • Crossref
    • PubMed
    • Export Citation
  • 6.

    Petit M, Beaudeux J-L, Majoux S, Hennequin C. Is a pre-analytical process for urinalysis required? Ann Biol Clin (Paris) 2017;75:519–24.

    • PubMed
    • Export Citation
  • 7.

    Maguire GA. Acidification and urinary calcium. Ann Clin Biochem 2010;47:183; author reply 183. doi:.

    • Crossref
    • PubMed
    • Export Citation
  • 8.

    Ng RH, Menon M, Ladenson JH. Collection and handling of 24-hour urine specimens for measurement of analytes related to renal calculi. Clin Chem 1984;30:467–71.

    • Crossref
    • PubMed
    • Export Citation
  • 9.

    Vassault A, Hulin A, Chapuzet E, Arnaud J, Giroud C. Membres du sous-groupe 2 analytique de la SFBC [Verification/validation of the performances of analytical method]. Ann Biol Clin (Paris) 2010;68:247–94.

  • 10.

    Larcher L, Lefevre G, Bailleul S, Daudon M, Frochot V. Importance of pre-analytical acidification for urinalysis with urinary crystals. Ann Biol Clin (Paris) 2017;75:525–30.

    • PubMed
    • Export Citation
  • 11.

    Pratumvinit B, Reesukumal K, Wongkrajang P, Khejonnit V, Klinbua C, Dangneawnoi W. Should acidification of urine be performed before the analysis of calcium, phosphate and magnesium in the presence of crystals? Clin Chim Acta 2013;426:46–50.

    • Crossref
    • PubMed
    • Export Citation
  • 12.

    Cohen R, Alkouri R, Tostivint I, Djiavoudine S, Mestari F, Dever S, et al. Impact of pH on urine chemistry assayed on Roche analyzers. Clin Lab 2017;63:1749–53.

    • PubMed
    • Export Citation
  • 13.

    Mazzachi BC, Teubner JK, Ryall RL. Factors affecting measurement of urinary oxalate. Clin Chem 1984;30:1339–43.

    • Crossref
    • PubMed
    • Export Citation
  • 14.

    Cochat P, Rumsby G. Primary hyperoxaluria. N Engl J Med 2013;369:649–58.

Purchase article
Get instant unlimited access to the article.
$42.00
Log in
Already have access? Please log in.


or
Log in with your institution

Journal + Issues

Clinical Chemistry and Laboratory Medicine ( CCLM) publishes articles on novel teaching and training methods applicable to laboratory medicine. CCLM welcomes contributions on the progress in fundamental and applied research and cutting-edge clinical laboratory medicine. It is one of the leading journals in the field, with an impact factor of over three. CCLM is the official journal of nine national clinical societies and associated with EFLM.

Search