Association between serum calcium and in-hospital mortality in critical patients with multiple myeloma: a cohort study

Figures & data

Figure 1. Flowchart of study population.

Table 1. Baseline demographic characteristics of the study population stratified by serum calcium.

Variables	Total (n = 262)	Serum calcium(mg/dL)			P
		< 8 (n = 80)	8 ∼ 9 (n = 108)	≥ 9 (n = 74)
Age, y	72.3 ± 11.0	71.0 ± 9.8	72.6 ± 11.0	73.4 ± 12.3	0.385
Sex, n (%)					0.145
male	166 (63.4)	54 (67.5)	72 (66.7)	40 (54.1)
female	96 (36.6)	26 (32.5)	36 (33.3)	34 (45.9)
Ethnicity, n (%)					0.578
white	179 (68.3)	53 (66.2)	74 (68.5)	52 (70.3)
black	46 (17.6)	12 (15)	22 (20.4)	12 (16.2)
other	37 (14.1)	15 (18.8)	12 (11.1)	10 (13.5)
Lowest hemoglobin (g/dL)	8.7 ± 1.9	8.1 ± 1.7	8.8 ± 1.8	9.3 ± 2.1	< 0.001
Lowest platelet count (×10^9/L)	129.5(70.2,187.0)	93.0(46.5,181.5)	131.5(84.5,179.5)	153.5(107.5,214.8)	0.004
Highest WBC (×10^9/L)	8.2 (5.0, 12.6)	6.7 (3.8, 11.8)	8.3 (5.5, 12.6)	8.9 (6.4, 12.8)	0.064
Highest BUN (mmol/L)	32.0 (20.2, 54.8)	29.5 (16.8, 50.0)	32.5 (20.8, 48.2)	34.5 (23.0, 69.5)	0.195
Highest creatinine (mg/dL)	1.5 (1.0, 2.9)	1.5 (1.0, 2.7)	1.5 (1.0, 3.0)	1.6 (1.1, 2.8)	0.614
Highest glucose (mg/dL)	141.5(116.2,174.0)	124.5(110.0,152.2)	146.5(122.8,174.8)	148.0(118.0,197.0)	0.009
Highest calcium (mg/dL)	8.4 ± 0.9	7.4 ± 0.4	8.5 ± 0.3	9.5 ± 0.6	< 0.001
Highest LDH (U/L)	293.0(195.0,425.0)	307.0(209.0,436.0)	251.0(204.5,347.0)	365.0(191.0,560.0)	0.148
Highest anion gap (mmol/L)	17.5 ± 5.9	16.1 ± 4.5	17.5 ± 6.5	18.9 ± 6.0	0.011
SOFA	3.2 ± 2.5	3.5 ± 2.5	3.2 ± 2.5	3.0 ± 2.4	0.342
SAPSII	39.2 ± 8.6	38.9 ± 8.6	39.2 ± 8.7	39.5 ± 8.5	0.917
Positive culture, %					0.086
no	158 (60.3)	54 (67.5)	63 (58.3)	41 (55.4)
yes	26 (9.9)	11 (13.8)	10 (9.3)	5 (6.8)
unknown	78 (29.8)	15 (18.8)	35 (32.4)	28 (37.8)

Notes: Data presented are mean ± SD, median (IQR), or N (%).

Abbreviations: SD: standard deviation; IQR: interquartile range; WBC, white blood cell; BUN: blood urea nitrogen; LDH, lactic dehydrogenase; SOFA: Sequential Organ Failure Assessment; SAPS II: Simplified Acute Physiology Score II.

Table 2. Association of covariates and in-hospital morality in patients with MM.

Variable	HR_95%CI	P-value
Sex
male vs. female	1.90 (1.08,3.35)	0.027
Age, y	1.04 (1.01,1.07)	0.006
Ethnicity:
white	Ref.
black	0.97 (0.43,2.21)	0.943
other	1.25 (0.61,2.57)	0.543
Lowest hemoglobin (g/dL)	1.05 (0.90,1.22)	0.547
Lowest platelet count (×10^9/L)	1.00 (1.00,1.00)	0.328
Highest WBC (×10^9/L)	1.01 (0.98,1.04)	0.618
Highest BUN (mmol/L)	1.01 (1.00,1.02)	0.020
Highest creatinine (mg/dL)	1.09 (0.99,1.20)	0.091
Highest calcium (mg/dL)	0.96 (0.70,1.33)	0.813
Highest glucose (mg/dL)	1.00 (1.00,1.00)	0.037
Highest LDH (U/L)	1.00 (1.00,1.00)	0.176
Highest anion gap (mmol/L)	1.08 (1.04,1.13)	< 0.001
SOFA	1.10 (1.00,1.20)	0.044
SAPSII	1.07 (1.03,1.10)	< 0.001

Table 3. Relationship between different serum calcium levels and in-hospital morality in different models.

Serum calcium	Non-adjusted Model		Model I		Model II
	HR (95% CI)	P-value	HR (95% CI)	P-value	HR (95% CI)	P-value
Calcium (mg/dL)	0.96 (0.70∼1.33)	0.813	0.97 (0.71∼1.33)	0.855	1.01 (0.71∼1.42)	0.973
<8 mg/dL	1.99 (0.97∼4.08)	0.061	1.93 (0.94∼3.96)	0.075	1.93 (0.89∼4.18)	0.098
8-9 mg/dL	Reference		Reference		Reference
≥9 mg/dL	2.75 (1.30∼5.81)	0.008	2.44 (1.15∼5.16)	0.020	2.72 (1.26∼5.88)	0.011

Notes: Data presented are HRs and 95% CIs.

Model I: adjusted for age, sex. Model II: adjusted for age, sex, ethnicity, urea nitrogen, glucose, SOFA and SAPSII.

Figure 2. The nonlinear relationship between serum calcium and in-hospital mortality in Multiple Myeloma in ICU. Adjusted for all covariates as model 2 (Calcium takes the upper limit of 98%).

Table 4. Threshold effect analysis of serum calcium level and the in-hospital mortality of MM using Cox regression models.

	HR	95%CI	P-value
Turning point (mg/dL)	8.400
Calcium < 8.4 mg/dL	0.270	0.106, 0.687	0.006
Calcium≥8.4 mg/dL	2.104	1.069, 4.142	0.031
Likelihood Ratio test			0.001

Notes: Data presented are HRs and 95% CIs.

Adjusted for age, sex, ethnicity, urea nitrogen, glucose, SOFA and SAPSII.