1. The clinical and laboratory features
Table 1 included the characteristics of all participants. Because the average length of hospital stay for AP patients was 14 days in Zhongda Hospital, and the average length of hospital stay in three-A class hospitals of Nanjing city was 8 days., we separated all data into three groups according to 8 and 14 days of length of hospital stay. Significant difference in the value distribution of gander (P = 0.017) and severity classification (P = 0.000) was found. We observed significant increases of MCH among three groups (30.02 ± 1.91, 30.21 ± 1.81, 30.92 ± 2.47 pg, P = 0.009). We also noticed significant difference of RBC among three groups (4.75 ± 0.45, 4.77 ± 0.56, 4.54 ± 0.62 ×1012/L, P = 0.007). There were no significant differences for other variables, including age, smoke, alcohol, cholecystectomy, WBC, HGB, MCV and MCHC.
Table 1. The clinical and laboratory data in whole population according to length of hospital stay
length of hospital stay (day)
|
≤ 8
N = 83
|
9–14
N = 95
|
≥ 15
N = 95
|
P-value
|
Gender (male, %)
|
52, 62.7%
|
66,69.5%
|
47, 49.5%
|
0.017*
|
Age (year)
|
44.0 ± 16.5
|
44.7 ± 16.1
|
46.7 ± 16.9
|
0.518
|
Smoke (n,%)
|
13, 15.7%
|
18, 18.9%
|
17, 17.9%
|
0.844
|
Alcohol (n,%)
|
11, 13.3%
|
16, 16.8%
|
13, 13.7%
|
0.754
|
Cholecystectomy (n,%)
|
3, 3.6%
|
6, 6.3%
|
6, 6.3%
|
0.666
|
Severity classification
|
|
|
|
0.000***
|
Mild (n, %)
|
78, 28.6%
|
87, 31.9%
|
80, 29.3%
|
|
Moderately (n, %)
|
1, 0.4%
|
1, 0.4%
|
0, 0%
|
|
Severely (n, %)
|
4, 1.5%
|
7, 2.6%
|
15, 5.5%
|
|
WBC (109/L)
|
10.49 ± 5.36
|
11.01 ± 4.64
|
11.27 ± 4.58
|
0.559
|
RBC (1012/L)
|
4.75 ± 0.45
|
4.77 ± 0.56
|
4.54 ± 0.62
|
0.007**
|
HGB (g/L)
|
142.49 ± 14.44
|
143.85 ± 15.97
|
139.34 ± 17.38
|
0.141
|
MCV (fL)
|
88.89 ± 5.25
|
89.16 ± 4.93
|
90.18 ± 5.06
|
0.197
|
MCH (pg)
|
30.02 ± 1.91
|
30.21 ± 1.81
|
30.92 ± 2.47
|
0.009**
|
MCHC (g/L)
|
337.41 ± 10.86
|
338.93 ± 12.28
|
342.97 ± 21.84
|
0.054
|
The demographic characteristics and laboratory parameters of study participants (n = 273) according to tertiles of length of hospital stay (day). WBC, white blood cell; RBC, red blood cell; HGB, hemoglobin; MCV, mean corpuscular volume; MCH, mean corpuscular hemoglobin; MCHC, mean corpuscular hemoglobin content. |
Due to the above interesting results between length of hospital stay and MCH, we separated all data into two groups according to the median number of MCH (Table 2). We observed significant increases of length of hospital stay between two groups (11.95 ± 7.03, 13.96 ± 8.18 days, P = 0.030). We also noticed significant difference of gender (P = 0.029), RBC (P = 0.000), MCV (P = 0.000), MCHC(P = 0.000) between two groups. There were no significant differences for other variables, including age, smoke, alcohol, cholecystectomy, WBC, HGB and severity classification.
Table 2. The clinical and laboratory data in whole population grouped according to MCH
MCH (pg)
|
≤ 30.3
N = 142
|
> 30.3
N = 131
|
P-value
|
Gender (male, %)
|
77, 54.2%
|
88, 67.2%
|
0.029*
|
Age (year)
|
44.3 ± 17.2
|
46.1 ± 15.7
|
0.363
|
Smoke (n,%)
|
21, 14.8%
|
27, 20.6%
|
0.207
|
Alcohol (n,%)
|
18, 12.7%
|
22, 16.8%
|
0.336
|
Cholecystectomy (n,%)
|
10, 7.0%
|
5, 3.8%
|
0.243
|
Severity classification
|
|
|
0.067
|
Mild (n, %)
|
132, 48.4%
|
113, 41.4%
|
|
Moderately (n, %)
|
1, 0.4%
|
1, 0.4%
|
|
Severely (n, %)
|
9, 3.3%
|
17, 6.2%
|
|
WBC (109/L)
|
10.65 ± 4.90
|
11.26 ± 4.78
|
0.294
|
RBC (1012/L)
|
4.83 ± 0.57
|
4.53 ± 0.50
|
0.000***
|
HGB (g/L)
|
140.20 ± 16.57
|
143.68 ± 15.43
|
0.074
|
MCV (fL)
|
86.60 ± 4.10
|
92.51 ± 4.19
|
0.000***
|
MCH (pg)
|
29.04 ± 1.38
|
31.88 ± 1.76
|
0.000***
|
MCHC (g/L)
|
335.36 ± 10.84
|
344.76 ± 19.14
|
0.000***
|
length of hospital stay (day)
|
11.95 ± 7.03
|
13.96 ± 8.18
|
0.030*
|
The demographic characteristics and laboratory parameters of study participants (n = 273) according to the median number of MCH. WBC, white blood cell; RBC, red blood cell; HGB, hemoglobin; MCV, mean corpuscular volume; MCH, mean corpuscular hemoglobin; MCHC, mean corpuscular hemoglobin content. |
2. The correlation between length of hospital stay and laboratory data in whole population
As shown in Fig. 1, the positive correlation between length of hospital stay and MCH was observed in these individuals (r = 0.172, P = 0.004). In order to further explore the correlation between length of hospital stay and other laboratory data, we did the correlation between length of hospital stay and other laboratory data in whole population (Table 3). Length of hospital stay correlated with gender (r= -0.123, P = 0.042), severity classification (r = 0.182, P = 0.003), WBC (r = 0.128, P = 0.034), RBC (r= -0.190, P = 0.002). Length of hospital stay had no correlation with age, smoke, alcohol, cholecystectomy, HGB, MCV, MCHC.
Table 3. The correlation between length of hospital stay and other laboratory data in whole population
|
correlation coefficient
|
P-value
|
Gender (male, %)
|
-0.123
|
0.042*
|
Age (year)
|
0.095
|
0.117
|
Smoke (n,%)
|
0.037
|
0.539
|
Alcohol (n,%)
|
0.018
|
0.763
|
Cholecystectomy (n,%)
|
0.044
|
0.467
|
Severity classification
|
0.182
|
0.003**
|
WBC (109/L)
|
0.128
|
0.034*
|
RBC (1012/L)
|
-0.190
|
0.002**
|
HGB (g/L)
|
-0.088
|
0.146
|
MCV (fL)
|
0.101
|
0.095
|
MCHC (g/L)
|
0.101
|
0.096
|
MCH (pg)
|
0.172
|
0.004**
|
WBC, white blood cell; RBC, red blood cell; HGB, hemoglobin; MCV, mean corpuscular volume; MCH, mean corpuscular hemoglobin; MCHC, mean corpuscular hemoglobin content. |
3. The correlation analyses in multiple linear regression analysis
The correlation analyses were carried out in all subjects. The basic demographic characteristics, such as gender, age and severity of AP, might influence length of hospital stay4. The laboratory parameters of study participants, such as WBC and HGB, might influence length of hospital stay as well. Therefore, gender, age, severity classification, WBC, HGB and MCH were included as independent variables in multiple linear regression analysis. We did two regression models to investigate the correlation between length of hospital stay and laboratory data (Table 4). We did linear regression based on gender, age, WBC, HGB and MCH in model 1, and model2 added severity classification on the basis of model 1. The results found that length of hospital stay was correlated with MCH in both model 1 and model 2 (beta = 0.248, P = 0.000 in model 1; beta = 0.212, P = 0.000 in model 2). Length of hospital stay was correlated with severity classification and gender independently (beta = 0.212, P = 0.000; beta = 0.211, P = 0.001; beta= -0.171., P = 0.015 respectively), as shown in Table 4.
Table 4. The factors related to length of hospital stay in AP patients in multivariable linear regression analysis
Model 1 (linear regression based on gender, age, WBC, HGB and MCH)
|
Unstandardized coefficients
B SE
|
Standard
Beta
|
P-value
|
Gender
|
-3.428
|
1.087
|
-0.219
|
0.002**
|
Age
|
0.031
|
0.028
|
0.067
|
0.264
|
WBC
|
0.244
|
0.092
|
0.155
|
0.009*
|
HGB
|
0.019
|
0.034
|
0.039
|
0.590
|
MCH
|
0.897
|
0.215
|
0.248
|
0.000***
|
Model 2 (linear regression based on gender, age, WBC, severity classification, HGB and MCH)
|
Unstandardized coefficients
B SE
|
Standard
Beta
|
P-value
|
Gender
|
-2.672
|
1.088
|
-0.171
|
0.015*
|
Age
|
0.022
|
0.027
|
0.048
|
0.415
|
WBC
|
0.155
|
0.094
|
0.098
|
0.101
|
HGB
|
-0.002
|
0.034
|
-0.005
|
0.943
|
Severity classification
|
2.729
|
0.796
|
0.211
|
0.001**
|
MCH
|
0.767
|
0.214
|
0.212
|
0.000***
|
WBC, white blood cell; HGB, hemoglobin; MCH, mean corpuscular hemoglobin |