Lack of correlation between calcium intake and serum calcium levels in stable haemodialysis subjects.
BACKGROUND
The relationship between calcium intake and serum calcium level in hemodialysis patients is poorly understood.


METHODS
We quantify total oral calcium intake using detailed 7-day food diaries with 294 patient days of observation in 42 stable, non-diabetic hemodialysis subjects.


RESULTS
Mean (SD) albumin-corrected serum calcium was 9.84 mg/dl (0.8). The albumin-corrected serum calcium was low (<8.4 mg/dl) in 2 patients, low-normal (8.4-9.49) in 9 patients, high-normal (9.5-10.2) in 18 patients and high (>10.2) in 13 patients. Mean (SD) total (diet plus binder) oral calcium intake was 1996 mg/day (1,020); 16 patients (38%) had a total calcium intake >2,000 mg/day. Calcium intake and serum calcium were poorly correlated (Spearman rank method), r = 0.14, p = 0.39. Median calcium intakes were similar in those with normal (1,990 mg/day), high-normal (1,926 mg/day) and high calcium groups (1,713 mg/day), p = 0.73 (Kruskal-Wallis), p = 0.29 (linear test for trend). Forty-one percent (11/27) of patients who had serum calcium in the normal range had a calcium intake greater than 2 g/day, while 11.5% had a calcium intake greater than 3 g/day. In subjects with a parathyroid hormone (PTH) concentration <300 pg/ml (n = 20), the correlation between calcium intake and either uncorrected serum calcium or albumin-corrected serum calcium was stronger, r = 0.45, p = 0.05 and r = 0.38, p = 0.10, respectively, though there remained wide variability in calcium intake.


CONCLUSIONS
Serum calcium is not a reliable indicator of calcium intake, especially at PTH > or = 300 pg/ml. An excessive calcium intake may coexist with a normal serum calcium level.
Byrne
Fiona N
FN
Department of Nutrition and Dietetics, Cork University Hospital, Cork, Ireland.
Kinsella
Sinead
S
Murnaghan
Dermot J
DJ
Kiely
Mairead
M
Eustace
Joseph A
JA
D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D002118:Calcium / Q000097:blood*; D002136:Calcium, Dietary / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood; D006435:Renal Dialysis; D012189:Retrospective Studies
D015415:Biomarkers; D002136:Calcium, Dietary; D010281:Parathyroid Hormone; D002118:Calcium