Pocket ObGyn – Women’s Health Epidemiology and Research
See Abbreviations
| US women’s mortality:Top causes for all females, all ages | |
| 1. Heart dz, 23.5%
2. Cancer, 22.1% 3. Stroke, 6.2% 4. Chronic lower respiratory dzs, 5.9% 5. Alzheimer dz, 4.7% |
6. Unintentional injuries, 3.6%
7. Diabetes, 2.7% 8. Influenza & pneumonia, 2.1% 9. Kidney dz, 2.1% 10. Septicemia, 1.5% |
| From CDC “Leading Causes of Death in Females”. 2010 data. http://www.cdc.gov/women/lcod/2010/index.htm. | |
| Annual US Gyn cancer deaths | ||
| Cause | Cases | Deaths |
| Endometrial | 41314 | 7456 |
| Ovarian | 20749 | 14621 |
| Cervical | 12280 | 4012 |
| Vulvar | 4159 | 865 |
| Vaginal | 1149 | 376 |
| From CDC “Leading Cause of Death in Females”. 2008 data, 10/15/12. | ||
| Epidemiology terms | |
| Sens | % w/ dz w/ positive result on a test |
| Spec | % w/o dz w/ negative result on a test |
| PPV | % w/ a positive test who actually have condition |
| NPV | % w/ a negative test who do not have the condition; PPV & NPV change w/ prevalence |
| Incid | Number of new events in a specific time period per pop at risk at the start of the time interval |
| Prevalence | Number of people w/ a dz at a point in time per pop at risk at that time |
| OR | Odds of an exposure w/ dz over odds in a control group; common for case-control studies |
| RR | Proportion of exposed who develop a condition over proportion of unexposed who develop a condition (Iexp/Iunexp); for cohort studies |
| AR | Probability of a medical event (as a % of all who could have the event). ARR = difference of ARs btw 2 groups |
| NNT | 1/the ARR in %; number of pts to treat for 1 prevented case (= 1 avoided risk outcome) |
| CI | If exp repeated 100´, truth is in this range 95´ (w/i the 95% CI). If CI crosses 1, the finding is not signif (= no effect) |
| Intention to treat analysis | Based on how subjects were originally randomized & includes all of them; no dropouts or problem pts subtracted from the groups |
| Type 1 error (a) | Rejecting the null hypothesis when it is actually true, causes you to believe there was an effect when there was not; usually set at p < 5% |
| Type 2 error (b) | Accepting the null hypothesis, when it is actually false; causes you to believe there was no effect when there actually was |
| Power | Ability of your study to detect a true difference (1 – b); often set at 80% |
| Calculating sensitivity, specificity, PPV, NPV | |||
| Dz + | Dz – | ||
| Test pos | a (true pos) | B (false pos) | PPV = [a/(a + b)] ´ 100 |
| Test neg | c (false neg) | D (true neg) | NPV = [d/(c + d)] ´ 100 |
| Sens = [a/(a + c)] ´ 100 | Spec = [d/(b + d)] ´ 100 | ||
| Types of studies | |
| Case series | What: Summary of cases & outcomes for an unusual event. Pro: Good for rare, interesting, or new conditions or rxs. Con: Only descriptive, not controlled, no causality. |
| Cohort | What: Follow exposed & control group for specific outcomes (in real time or after the outcome has already occurred). Looks forward for outcome. Define by exposure ® eval outcome.
Pro: Can be retrospective (“historical cohort”) or prospective. Con: No causality; prospective is expensive & lengthy. |
| Case control | What: Search for prior exposure in cases (w/ condition) compared w/ controls (w/o condition). Looks backward.
Pro: Can be run quickly w/ existing databases. Good for rare conditions. Con: No causality; matching cases & controls can be difficult. |
| RCT | What: Follow randomized groups of pts w/ rx or placebo to assess outcomes/complications. A “true experiment.”
Pro: Level 1 evid; gold std for clinical research. Con: Often difficult to recruit & expensive. May not be feasible or ethical for certain clinical questions (eg, many obstetrical concerns). |
Phases of Clinical Trials (Understanding Clinical Trials, NIH, clinicaltrials.gov)
- Phase 1: Tests an experimental drug or rx in a small group of people (10–80) to evaluate safety, determine a dosage, & identify side
- Phase 2: The experimental study drug or rx is given to a larger group of people (100–300) to see if it is effective & to further evaluate
- Phase 3: The experimental study drug or rx is given to large groups (1000–3000) to confirm effectiveness, monit side effects, & collect safety
- Phase 4: Postmarketing review of risk/benefit & unexpected