The sensitivity of high levels of prostate specific antigen (PSA ³ 4.0 ng/ml) to identify prostate cancer has ranged fro

[answerhappygod]

The sensitivity of high levels of prostate specific antigen (PSA
³ 4.0 ng/ml) to identify prostate cancer has ranged from 35% to 71%
and specificity from 63% to 91%, with resulting false-positive
rates of 20% to 68%. A cohort study to evaluate the relationship of
serum retinol (vitamin A) levels to prostate cancer was conducted
by Mondul and collaborators. They included close to 30,000 smoking
men aged 50-69 years at baseline. The hazard ratio (relative risk)
of prostate cancer associated with the upper quintile of serum
retinol – compared with that of the lowest quintile – was found to
be 1.13 as measured in the 3-year follow-up visit. This exercise
will assume that this is the true relative risk for the association
of the 5th vs the 1st quintile of retinol.
The table summarizes some of the study results. For the purposes of
this exercise, the number of person-years given in the paper by
Mondul et al. was considered as number of persons.
Incidence rates and relative risks of prostate cancer according
to extreme quintiles of serum retinol, 1985-2006, from the
Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study.
Retinol levels
No. of cases
No. of persons
Incidence/1000
Relative risk
Quintile 1
312
66,010
4.73
1.00
Quintile 5
377
70,747
5.33
1.13
Assuming sensitivity and specificity of 0.70 and 0.90 for the
ascertainment of prostate cancer in this study, and further
assuming that these levels are the same for both quintiles
calculate the biased relative risk using the data in the table
above as the gold standard (true values). Define the type of
misclassification based on the answer.