3. (medicine) 40 total points) Hypertension is a tuedical conlition in which the

Question

3. (medicine) 40 total points) Hypertension is a tuedical conlition in which the blood pressure is chronically elevated. Persistent hypertension is one of the risk facturs for strokes, heat attack3. heart failure and arterial aneut ysm, and is a leading ranse of thronic renal failure; as of 1999, it was estimated that 29% of American adults were v pertensive, and a U S public Lea th gril in 2000 was to lower this rate to 16% by 2010 (thia goal h s not yet been uien Diet and exer go a long way to lower blood prease, bul drugs are also scmetinue needed (particuliar how hard it is to get Anericans to exercise and eat in a lealttier w cise can The online reference Wikipedia notes that Captopri is an augictensin-conver ing inlibitor used for the trearment of kypertension and some ty pes of congestive heat fnilure. Capto- pril was the first ACE inhibitor devek ped and was considered a breakthrougt boih becanse of its huvel michaism of acticn and also heeause of the revolutionary development provss. The de- velopiment of Captopril was among the carliest successes uf the revolutionary coucept of structure- ased drug desin. The renin angioteusir-aldosteroue system (a hormone systeni late long-term blood pressre and blud volume in the hody) had beeu extensively studied in the mid-210th cent iry, aud it had been docided that this system prescntei several opportue targets i. the development of novel treatmerts for hyper ension. that helps regu- Captopril was ?eveloped in the id 197Os; acGregor et al. (1979, Brilish Medieal Jaumal) pub- lished th e results of a cliical trial on its effecis. Systolic bloo? pressure (in mmHg) were measued for n 12 representatively-chosen y pertencive patients, before aud after teking Capto long enough time pericd for the drug to work; the results are given in Table 1. Note: I've ue) ? bit o: d ilen elt notation beliw thar what we used in cinse his is to give you practit in the skill of reading statistiea diseussions in sotrces uth originally learued the concepts.) in sources aher than the classes and lextbooks ir which you bject A R C D E F C H I J KLIMean SD Before 200 174 19s 170 179 182 1932 185 155 160 210 185.3 17.1 After 191 iro 177 167 159 151 176 183 159 115 146 177 166.8 14.9 Difference!+9 +1 +2 1 13-20 ?31 +17-+26 +26--10 -t23 +33. 18.6 10.1- Table 1: Before and after resnlus for 12 hypertensive petients treated with Coptopri propriate to generalize here, and explicitly icentity that population. Is this estimated effect large in clinical terms Attach a standard error to your estimated effert, and construct a 95% confidence interval fr ?. Is the tstimated effect statistically significari? what do you conclude about Captopril's usefulness in treating hyperter sion? Explain briedy. f20 pwiuls! (a) Estimate the average effect ? of Captopril in the population to which you believe it's ap-

Explanation / Answer

(a)
The average effect (reduction in Systolic blood pressure) of Captopril is 18.6 mmHg
The population is American hypertensive adults.
The estimated effect of 18.6 mmHg is large in clinical terms.

The standard deviation of difference is 10.1
Standard error of the mean difference = 10.1 / sqrt(12) = 2.9156
Degree of freedom = n-1 = 12 - 1 = 11
Critical value of t at 95% confidence level and df = 11 is 2.2
95% confidence interval is,
(18.6 - 2.2 * 2.9156, 18.6 + 2.2 * 2.9156)
(12.18568, 25.01432)
As, 95% confidence interval does not contains 0, the estimated effect is statistically significant.
As, the estimated effect is statistically significant, Captopril is useful in treating hypertension with mean effect of 18.6 mmHg and between 12.18568 and 25.01432) with 95% confidence.

(b)
(i)
Variance(diff) = Variance(After - Before) = Variance(After) + Variance(Before) - 2 Covariance(Before, After)

As, before and after Systolic blood pressure have high positive correlation, Covariance(Before, After) is high.
High Covariance(Before, After) leads to low Variance(diff) and consequently low SD of the differences.

It is difficult to find homogeneous hypertensive patients in all respects and hence completely randomized design is less accurate than the paired design given in the problem where the same subjects were involved in before and after treatments.

(ii)
The diff is positive correlated with before. This means as Systolic blood pressure before treatment increases, the difference of before and after increases.
So, there seems to have a larger effect for people with high initial blood pressure than low  initial blood pressure.

Related Questions

Navigate

• Browse (All)
• Browse 3
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.