Preventive Health Care Screening. Miriam Rabkin, MD. Preventive Health Care Screening. Screening basics: clinical epidemiology Screening guidelines Cancer screening: some examples. Screening Basics. What does “screening” mean? What do we screen for? risk factors for disease
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Miriam Rabkin, MD
does more screening =
better health care?
Although the combination ELISA/Western Blot test for HIV has extremely high sensitivity and specificity, predictive value is dependent on prevalence.
High risk population: prevalence = 40%
PPV = 0.985 NPV = 0.993
Low risk population: prevalence = 0.01% PPV = 0.0098 NPV = 0.999
Length bias is the preferential detection of slowly progressive disease
A: good evidence to support the recommendation that the condition be considered in a periodic health exam
B: fair evidence to support the recommendation
C: insufficient evidence to recommend for or against
D: fair evidence to recommend exclusion
E: good evidence to recommend exclusion
A: routine Pap smears for all women who have ever been sexually active and who have a cervix
B: frequency - at least every three years
There is little evidence that more frequent screening is beneficial (except in HIV-infected patients). May be effective in HPV-infected patients.
C: discontinue Pap smears at age 65 if patient has had regular normal Paps in past
C: HPV infection screening
Case for screening with annual DRE (digital rectal exam):
None. There is no evidence to support this screening strategy.
Case for screening with FOBT (fecal occult blood testing):
Case for screening with sigmoidoscopy:
> No randomized trials !
> Selby et al. 1992: case-control study of rigid sigmoidoscopy screening. Odds ratio for dying of distal colorectal cancer was 0.41 (0.25-0.69) for those screened. No protective effect on dying of proximal colorectal cancer.
NB: There are no studies evaluating whether screening colonoscopy alone reduces the incidence or mortality of CRC in patients at average risk.
B: For all normal risk persons age > 50
1) annual FOBT (with colonoscopy if + )
2) flexible sigmoidoscopy every 3-5 years
C: DRE, BE, routine colonoscopy
Preclinical detectable period?
D: routine screening with ultrasound or serum tumor markers is not recommended
C: there is insufficient evidence to recommend for or against screening women at increased risk
meta-analysis of 13 studies (the 8 RCTs and 5 case-control studies)
RR for breast cancer mortality
women 50-74 0.74 (0.66 - 0.83)
women 40-49 0.93 (0.76 - 1.13)
7-9 years of follow-up 1.02 (0.82 - 1.27)
10-12 years 0.83 (0.65 - 1.06)