Received April 13, 2007
Accepted on February 19, 2008

CLINICAL RESEARCH

Pitfalls of Measuring Total Blood Calcium in Patients with CKD

Cédric Gauci ^*, Olivier Moranne ^*, Bruno Fouqueray , Renaud de la Faille ^*, Gérard Maruani ^*, Jean-Philippe Haymann , Christian Jacquot ^*, Jean-Jacques Boffa , Martin Flamant , Jérôme Rossert ^*||, Pablo Urena ^¶, Bénédicte Stengel ^**, Jean-Claude Souberbielle , Marc Froissart ^*||, Pascal Houillier ^*||1, and NephroTest Study Group

*Department of Physiology and Nephrology, Hôpital Européen George Pompidou, Assistance Publique-Hôpitaux de Paris; Faculté de Médecine, Université Paris Descartes; Department of Physiology and Nephrology, Hôpital Tenon, Assistance Publique-Hôpitaux de Paris; Faculté de Médecine, Université Pierre et Marie Curie; and INSERM U702; ||INSERM U872; and Department of Physiology, Hôpital Necker, Assistance Publique-Hôpitaux de Paris, Paris; INSERM U780; and **Université Paris-Sud, IFR 69, Villejuif; and ¶Clinique de l’Orangerie, Aubervilliers, France

¹ To whom correspondence should be addressed. E-mail: pascal.houillier{at}egp.aphp.fr;.

	Abstract

Disorders of mineral and bone metabolism are prevalent in patients with chronic kidney disease (CKD). The recent National Kidney Foundation Kidney Disease Outcomes Quality Initiative (K/DOQI) guidelines recommend that blood calcium (Ca) be regularly measured in patients with stages 3 to 5 CKD. The Kidney Disease: Improving Global Outcomes (KDIGO) position states that the measurement of ionized Ca (iCa) is preferred and that if total Ca (tCa) concentration is used instead, then it should be adjusted in the setting of hypoalbuminemia. In 691 consecutive patients with stages 3 to 5 CKD, we compared the ability of noncorrected and albumin-corrected tCa concentration to identify low, normal, or high iCa concentration. The agreement between noncorrected or albumin-corrected tCa and iCa was only fair. The risk for underestimating ionized calcium was independently increased by a low total CO₂ concentration when either noncorrected or albumin-corrected Ca was used and by a low albumin concentration only when noncorrected tCa was used. The risk for overestimating iCa was increased by a low albumin concentration only when albumin-corrected Ca was used. In conclusion, albumin-corrected tCa does not predict iCa better than noncorrected tCa. Moreover, both noncorrected and albumin-corrected tCa concentrations poorly predict hypo- or hypercalcemia in patients with CKD.