Variables | Pilot group (n=4907) | Control group (n=9814) | P value | Standardised differences* |

Sex, n (%) | <0.767 | |||

Male | 2650 (54.00) | 5322 (54.23) | 0.005 | |

Female | 2257 (46.00) | 4492 (45.77) | 0.005 | |

Age (years), mean±SD | 62.44±10.69 | 62.44±10.57 | 0.983 | 0.000 |

Number of comorbidities, n (%) | 0.966 | |||

0 | 1800 (36.68) | 3605 (36.73) | 0.001 | |

1 | 1020 (20.79) | 2043 (20.82) | 0.001 | |

≥2 | 2087 (42.53) | 4166 (42.45) | 0.002 | |

Number of complications, n (%) | 0.964 | |||

0 | 1343 (27.37) | 2689 (27.40) | 0.001 | |

1 | 1473 (30.02) | 2964 (30.20) | 0.004 | |

≥2 | 2091 (42.61) | 4161 (42.40) | 0.004 | |

Types of medical insurance, n (%) | 0.756 | |||

Urban employees | 4725 (96.29) | 9460 (96.39) | 0.005 | |

Urban residents | 182 (3.71) | 354 (3.61) | 0.005 | |

Grade of hospitals, n (%) | 0.990 | |||

Primary hospitals | 1252 (25.51) | 2498 (25.45) | 0.001 | |

Secondary hospitals | 2678 (54.58) | 5368 (54.70) | 0.006 | |

Tertiary hospitals | 977 (19.91) | 1948 (19.85) | 0.002 |

*For continuous variables, the standardised differences is defined as

where and indicate the sample mean of the covariates in pilot and control groups, respectively, while and denote the sample variance. For categorical variables, the standardised differences is defined as

where

*P*and_{pilot}*P*denote the prevalence of variables in the two groups._{control}PSM , propensity score matching .