Skip to main content
. 2012 Apr 20;12:288. doi: 10.1186/1471-2458-12-288

Table 3.

Impacts of price adjustments on monthly expenditures on ACEIs, ARBs and overall renin-angiotensin drugs

Dependent variables Time period Factored ARIMA model* Independent variables† Coefficients‡ p value
Primary analyses
ACEIs
 Jan 1997 toDec 2008
 p = (1)(12);
 Constant
 4,509,908
 <0.0001
    q = (1)(9)
 Baseline trend
 66,568
 <0.0001
 
  
  
 PA2000 level change
 -592,252
 0.0151
 
  
  
 PA2003 level change
 -1,255,287
 <0.0001
 
  
  
 PA2004 trend change
 -96,582
 <0.0001
 
  
  
 PA2006 level change
 -1,545,767
 <0.0001
 
  
  
 CNY
 -351,216
 0.0029
ARB
 Feb 1998 toDec 2008
 p = (12);
 Baseline trend
 92,537
 <0.0001
    q = (2)
 PA2001 trend change
 160,472
 <0.0001
 
  
  
 PA2004 trend change
 -120,338
 <0.0001
 
  
  
 PA2007 trend change
 194,043
 <0.0001
 
  
  
 CNY
 -577,052
 0.0220
Renin-angiotensin drugs
 Jan 1997 to Dec 2008
 p = (6);
 Constant
 3,753,898
 <0.0001
    q = (6)
 Baseline trend
 152,800
 <0.0001
 
  
  
 PA2001 trend change
 110,259
 <0.0001
 
  
  
 PA2004 trend change
 -133,325
 <0.0001
 
  
  
 PA2006 level change
 -2,224,884
 <0.0001
 
  
  
 PA2007 trend change
 173,056
 <0.0001
 
  
  
 CNY
 -1,108,357
 0.0011
Subgroup analyses for ACEIs
Patented ACEIs
 Jan 1997 to
Dec 2008
 p = (1)(6,12);
 Constant
 497,488
 <0.0001
    q = (1)
 Baseline trend
 12,684
 <0.0001
 
  
  
 PA2001 level change
 189,675
 0.0281
 
  
  
 PA2007 trend change
 25,478
 0.0088
 
  
  
 CNY
 -116,498
 0.0011
Off-patent ACEIs
 Jan 1997 to
Dec 2008
 p = (1)(12);
 Constant
 3,987,107
 <0.0001
    q = (1)(9)
 Baseline trend
 45,221
 <0.0001
 
  
  
 PA2000 level change
 -380,037
 0.0251
 
  
  
 PA2003 level change
 -1,022,868
 <0.0001
 
  
  
 PA2004 trend change
 -70,970
 <0.0001
 
  
  
 PA2006 level change
 -1,675,618
 <0.0001
 
  
  
 PA2007 level change
 -689,097
 0.0002
 
  
  
 CNY
 -239,858
 0.0034
Off-patent original branded ACEIs
 Jan 1997 to
Dec 2008
 p = (1)(12);
 Constant
 3,195,426
 <0.0001
    q = (1)(9)
 Baseline trend
 12,121
 0.0081
 
  
  
 PA2000 level change
 -266,177
 0.0271
 
  
  
 PA2003 level change
 -498,038
 <0.0001
 
  
  
 PA2004 trend change
 -46,182
 <0.0001
 
  
  
 PA2006 level change
 -575,144
 <0.0001
 
  
  
 CNY
 -182,498
 0.0019
Off-patent generic ACEIs
 Jan 1997 to
Dec 2008
 p = (1)(12);
 Constant
 985,881
 0.0269
    q = (1)(5,9)
 Baseline trend
 27,153
 0.0008
 
  
  
 PA2003 level change
 -525,353
 <0.0001
 
  
  
 PA2006 level change
 -1,092,328
 <0.0001
      PA2007 level change -524,951 <0.0001

*Factored ARIMA model is represented by p, d, q: p, auto-regressive order; d, differencing order; q, moving-average order; seasonal order is represented by p = (12), d = (12) or q = (12). Take patented ACEIs as an example. The autoregressive operator represented by p = (1)(6,12) means

(1-θ 1 B) (1-θ 6 B 6 -θ 12 B 12 ).

†Parsimonious models were adopted, and therefore, only significant independent variables were incorporated into the model.

‡The unit of the regression coefficient is NT$ (NT$, New Taiwan Dollars; at an exchange rate of NT$30.39 to US$1 on June 30, 2008)

ACEIs, angiotensin-converting enzyme inhibitors; ARBs, angiotensin receptor blocker; ARIMA, auto-regressive integrated moving-average;

CNY, Chinese new year; PA2000, price adjustment implemented on April 1, 2000; PA2001, price adjustment implemented on April 1, 2001; PA2003, price adjustment implemented on March 1, 2003; PA2004, price adjustment implemented on November 1, 2004; PA2005, price adjustment implemented on September 1, 2005; PA2006, price adjustment implemented on November 1, 2006; PA2007, price adjustment implemented on September 1, 2007.