Table 2.

Interrupted time series (ITS) analyses for total costs per case, out-of-pocket payments per case, length of stay and in-hospital mortality rate of hospitalized patients covered by the urban employee basic medical insurance before and after the DIP reform

Indicators	Baseline monthly slope (β1)		Step change (β2)		Monthly slope change (β3)		Constant (β0)
	Estimate (95%CI)	P value	Estimate (95%CI)	P value	Estimate (95%CI)	P value	Estimate (95%CI)	P value
All patients
ln (Total costs per case)	-0.003 (-0.006, 0.000)	0.067	0.041 (0.008, 0.074)	0.016	0.005 (0.000, 0.010)	0.060	7.820 (6.908, 8.732)	0.000
ln (Out-of-pocket payments per case)	0.016 (-0.015, 0.047)	0.301	-0.298 (-0.661, 0.065)	0.105	-0.011 (-0.074, 0.051)	0.713	-2.228 (-20.673, 16.217)	0.808
Length of stay	-0.051 (-0.079, -0.023)	0.001	0.271 (-0.019, 0.561)	0.066	-0.008 (-0.051, 0.035)	0.709	-3.287 (-12.478, 5.903)	0.472
In-hospital mortality rate	-0.015 (-0.033, 0.003)	0.093	-0.084 (-0.278, 0.110)	0.385	0.005 (-0.026, 0.036)	0.739	-2.359 (-7.588, 2.871)	0.366
Age groups: younger vs older
Age group: younger (18–64)
ln (Total costs per case)	0.001 (-0.003, 0.004)	0.678	0.029 (-0.005, 0.063)	0.092	-0.001 (-0.006, 0.003)	0.584	7.794 (6.695, 8.894)	0.000
ln (Out-of-pocket payments per case)	0.036 (0.006, 0.067)	0.022	-0.325 (-0.731, 0.081)	0.114	-0.014 (-0.094, 0.066)	0.723	-7.160 (-23.097, 8.776)	0.368
Length of stay	-0.019 (-0.055, 0.017)	0.286	0.351 (-0.005, 0.706)	0.053	-0.058 (-0.111, -0.004)	0.035	-2.603 (-11.348, 6.142)	0.550
In-hospital mortality rate	-0.011 (-0.020, -0.002)	0.021	-0.108 (-0.203, -0.013)	0.027	0.012 (-0.000, 0.024)	0.058	1.075 (-1.372, 3.522)	0.378
Age group: older (65 +)
ln (Total costs per case)	-0.001 (-0.003, 0.001)	0.255	0.028 (0.006, 0.049)	0.013	0.005 (0.002, 0.008)	0.002	10.273 (9.845, 10.701)	0.000
ln (Out-of-pocket payments per case)	0.004 (-0.021, 0.029)	0.734	-0.163 (-0.423, 0.097)	0.211	-0.008 (-0.058, 0.041)	0.738	2.227 (-6.863, 11.317)	0.622
Length of stay	-0.059 (-0.081, -0.038)	0.000	0.360 (0.101, 0.619)	0.008	0.022 (-0.013, 0.057)	0.205	10.346 (3.064, 17.627)	0.007
In-hospital mortality rate	-0.013 (-0.038, 0.012)	0.303	-0.240 (-0.481, 0.001)	0.051	-0.030 (-0.080, 0.020)	0.229	-8.115 (-16.201, -0.028)	0.049
Age groups: young-old vs oldest-old
Age group: young-old (65–79)
ln (Total costs per case)	0.000 (-0.002, 0.003)	0.923	0.026 (-0.007, 0.060)	0.122	0.003 (-0.001, 0.006)	0.106	10.158 (9.511, 10.804)	0.000
ln (Out-of-pocket payments per case)	0.011 (-0.016, 0.038)	0.400	-0.134 (-0.422, 0.154)	0.351	-0.031 (-0.085, 0.024)	0.259	0.394 (-7.830, 8.617)	0.923
Length of stay	-0.038 (-0.053, -0.022)	0.000	0.249 (-0.017, 0.515)	0.066	-0.025 (-0.047, -0.004)	0.024	7.559 (0.997, 14.122)	0.025
In-hospital mortality rate	-0.010 (-0.026, 0.005)	0.184	-0.144 (-0.321, 0.033)	0.108	-0.014 (-0.040, 0.012)	0.274	-4.721 (-9.840, 0.397)	0.070
Age group: oldest-old (80 +)
ln (Total costs per case)	-0.001 (-0.004, 0.002)	0.524	0.028 (-0.008, 0.063)	0.127	0.006 (0.001, 0.010)	0.015	9.398 (8.598, 10.198)	0.000
ln (Out-of-pocket payments per case)	-0.010 (-0.028, 0.008)	0.255	-0.012 (-0.264, 0.240)	0.923	0.025 (-0.001, 0.051)	0.057	5.781 (0.401, 11.161)	0.036
Length of stay	-0.097 (-0.152, -0.041)	0.001	0.622 (-0.002, 1.246)	0.051	0.107 (0.011, 0.204)	0.030	7.972 (-5.376, 21.320)	0.233
In-hospital mortality rate	-0.039 (-0.096, 0.019)	0.182	-0.233 (-0.836, 0.370)	0.437	-0.009 (-0.115, 0.098)	0.869	-5.736 (-22.689, 11.216)	0.497

DIP denoted the Diagnosis-Intervention Packet payment reform; CI the confidence interval. Total costs and out-of-pocket payments were adjusted to 2019 considering inflation using annual consumer price index of China. Total costs per case and out-of-pocket payments per case were logarithmically transformed in the ITS model. ITS analyses controlled for number of discharge cases, age, sex, Charlson Comorbidity Index of patients, hospital level, hospital ownership and seasonality, with robust standard errors