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Decreased Rate of Coronary Restenosis After Lowering of Plasma Homocystine Levels

Decreased Rate of Coronary Restenosis After Lowering of Plasma Homocystine Levels. Seminar 25 Elise Miller. A few definitions…. Plasma Homocystine- blood amino acid influenced by genetics and diet. Restenosis- renarrowing of an artery after angioplasty caused by fat or cholesterol buildup.

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Decreased Rate of Coronary Restenosis After Lowering of Plasma Homocystine Levels

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  1. Decreased Rate of Coronary Restenosis After Lowering of Plasma Homocystine Levels Seminar 25 Elise Miller

  2. A few definitions…. • Plasma Homocystine- blood amino acid influenced by genetics and diet. • Restenosis- renarrowing of an artery after angioplasty caused by fat or cholesterol buildup. • Angioplasty- opens blocked arteries by the inflation of a tiny balloon.

  3. Which Alternative Makes Sense? Luminal Diameter: Ha: µF>µP Ha: µF<µP ↑ Stenosis: Ha: µF>µP Ha: µF<µP ↑ Late Loss Luminal Diameter: Ha: µP>µF Ha: µP<µF ↑

  4. T-test Construction • When dealing with two means and unequal sample sizes:

  5. Degrees of Freedom • Large, complicated formula…. d.f.= (s12/n1 + s22/n2) ÷ (((s12/n1)2 ÷ (n1-1)) + ((s22/n2)2 ÷ (n2-1))) • For our purposes it is assumed that df=160 (somewhere between n1-1 and n1+n2-2)

  6. Practice • Find the T-statistic for Luminal Diameter • Given info: Folate Group: sample n= 92 sample mean= 1.72 sample s.d= .76 Placebo Group: sample n=85 sample mean=1.45 sample s.d= .88

  7. Plug in the values… (1.72-1.45)/sqrt[(.76^2/92)+(.88^2/85)] t=2.1765 • This value gets inputted into Minitab to easily find the P-value.

  8. T-Values • Luminal Diameter: T=2.1765 • Stenosis: T=-2.226 • Late Loss Luminal Diameter: T=-1.860

  9. Reasoning… • Luminal Diameter: -positive value, wider arteries are better • Stenosis: -Negative value, after treatment the severity of stenosis decreased. • Late Loss Luminal Diameter: -Negative value, control is being compared to treatment group -the negative shows that the luminal diameter was smaller in the control group.

  10. What about the P-values? • Based on the t-statistics, what may the p-values be? (large n value) • Luminal Diameter: T=2.1765 • Stenosis: T=-2.226 • Late Loss Luminal Diameter: T=-1.860

  11. P-value Comparisons • Luminal Diameter: given: p=.02 by hand: p=.0155 • Stenosis: given: p=.01 by hand: p=.01371 • Late Loss Luminal Diameter: given: p=.03 by hand: p=.0324

  12. Potential Bias? • Most studies published in medical journals tend to have little or no bias • A few people did drop out of the study, but most likely did not create any impact on the results.

  13. Research Conclusions • Folate treatment is beneficial compared to placebo treatment group. • Treatment reduced restenosis, and late loss luminal diameter. • Treatment increased luminal diameter post-op.

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