title: A comparison of total calcium, corrected calcium, and ionized calcium concentrations as indicators of calcium homeostasis among hypoalbuminemic dogs requiring intensive care.
abstract: OBJECTIVE
  (1) To evaluate whether total calcium (tCa) correlates with ionized calcium (iCa) in hypoalbuminemic dogs; (2) to evaluate whether calcium adjusted for albumin (Alb), or total protein (TP), or both accurately predict iCa concentrations and hence can be used to monitor calcium homeostasis in critically ill hypoalbuminemic dogs; and (3) to evaluate factors associated with any potential discrepancy in calcium classification between corrected total and ionized values.
  
  
  METHODS
  Prospective observational clinical study.
  
  
  METHODS
  Small animal intensive care unit in a veterinary medical teaching hospital.
  
  
  METHODS
  Twenty-eight client-owned dogs with hypoalbuminemia.
  
  
  METHODS
  None.
  
  
  RESULTS
  iCa was determined using ion-specific electrode methodology, on heparinized plasma. The tCa concentration was adjusted for Alb and TP using published equations. In total 29% (8/28) of the hypoalbuminemic, critically ill dogs in this study were hypocalcemic at intensive care unit admission, as determined by iCa measurement. Corrected calcium values failed to accurately classify calcium status in 67.9% and 64.3% of cases, according to whether the Alb-adjusted or TP-adjusted values, respectively, were used. The sensitivity and specificity of the tCa to evaluate hypocalcemia was 100% and 47%, respectively. The sensitivity and specificity of the correction formulae were 37.5% and 79% for the Alb-adjusted values and 37.5% and 74% for TP-adjusted values. tCa overestimated the presence of hypocalcemia and underestimated the presence of normocalcemia, while corrected calcium values overestimated the presence of normocalcemia and underestimated the presence of hypocalcemia.
  
  
  CONCLUSIONS
  Calcium homeostasis in hypoalbuminemic critically ill dogs should be evaluated by iCa concentrations rather than tCa or calcium adjusted for Alb or TP. Given that tCa has 100% sensitivity for detecting hypocalcemia in this population it is recommended that all hypoalbuminemic and critically ill patients with low tCa should be evaluated with an iCa measurement.
authors.affiliation: Department of Veterinary and Medicine and Surgery, University of Missouri, Columbia, MO 65211, USA. claire.sharp@tufts.edu
authors.forename: Claire R
authors.initials: CR
authors.lastname: Sharp
authors.forename: Marie E
authors.initials: ME
authors.lastname: Kerl
authors.forename: F A
authors.initials: FA
authors.lastname: Mann
mesh_terms: D000818:Animals; D001798:Blood Proteins; D002118:Calcium / Q000097:blood*; D003422:Critical Care / Q000379:methods; D004283:Dog Diseases / Q000097:blood* / Q000209:etiology; D004285:Dogs; D005260:Female; D006706:Homeostasis; D034141:Hypoalbuminemia / Q000097:blood / Q000150:complications; D006996:Hypocalcemia / Q000097:blood / Q000150:complications / Q000662:veterinary*; D007019:Hypoproteinemia / Q000097:blood / Q000662:veterinary*; D008297:Male; D011446:Prospective Studies; D012582:Schools, Veterinary; D012680:Sensitivity and Specificity; D012709:Serum Albumin
chemical_list: D001798:Blood Proteins; D012709:Serum Albumin; D002118:Calcium