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Table 3 Impacts of price adjustments on monthly expenditures on ACEIs, ARBs and overall renin-angiotensin drugs

From: Impact of drug price adjustments on utilization of and expenditures on angiotensin-converting enzyme inhibitors and angiotensin receptor blockers in Taiwan

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

  1. *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
  2. (1-θ 1 B) (1-θ 6 B 6 12 B 12 ).
  3. Parsimonious models were adopted, and therefore, only significant independent variables were incorporated into the model.
  4. 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)
  5. ACEIs, angiotensin-converting enzyme inhibitors; ARBs, angiotensin receptor blocker; ARIMA, auto-regressive integrated moving-average;
  6. 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.