Background: In the Minnesota Colon Cancer Control Study, annual fecal occult blood testing reduced mortality from colorectal cancer by at least 33.4%. Some attribute a large part of this reduction to ...chance detection of cancers by colonoscopies; rehydration of guaiac test slides greatly increased positivity and consequently the number of colonoscopies performed. This study was conducted to determine how much of the reduction resulted from chance detection. Methods: We used a mathematical model developed by Lang and Ransohoff to estimate the proportion of the 33.4% mortality attainable by chance alone. Applying the model requires the specification of five parameters: duration of follow-up, rate of compliance with fecal occult blood testing, rate of compliance with colonoscopy, positivity rate, and efficacy of colonoscopy in reducing colorectal cancer mortality. We took values for four of the five parameters directly from the Minnesota study. For the fifth parameter, efficacy of colonoscopy, we selected a value of 60%, based on the conclusions of another study. Whereas the Lang-Ransohoff model selects persons for colonoscopy by chance alone, those with bleeding cancers would also be selected by sensitive fecal occult blood testing. We therefore adjusted the result of the Lang-Ransohoff model for this dual detectability. Results: We found that 16%–25% of the reduction in colorectal cancer deaths effected by fecal occult blood testing in the Minnesota study was due to chance detection; the remainder was due to sensitive detection. Conclusion: Chance played a minor role in the detection of colorectal cancers by fecal occult blood testing in the Minnesota study.
For deaths during the first 13 years of follow-up of the Minnesota Colon Cancer Control Study, an expert committee using numerous medical documents, and a nosologist using only the death certificate ...independently determined whether colorectal cancer caused the death and, if not, whether the disease was present at death. Deaths due to colorectal cancer numbered 318 according to the nosologist and 323 according to the committee, a discrepancy of 1.5%, which is similar in magnitude to that in three previous studies. The nosologist and committee agreed that colorectal cancer caused the death in each of 290 individual cases; they disagreed widely on the number of deaths from other causes but with colorectal cancer.
If it is important to know only the gross number of deaths from colorectal cancer, then the death certificate alone appears to be sufficiently accurate; if it is important to know the cause of death of individual subjects or the number dying from other causes but with colorectal cancer, then the expert committee method provides more accurate information.
Full text
Available for:
IJS, IMTLJ, KILJ, KISLJ, NUK, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Data from the 1971-1972 National Health and Nutrition Examination Survey were used to examine the associations between specific cataract types and age, race, sex, number of years spent in school, ...diabetes, systolic blood pressure, urban versus rural residence, and average daily ultraviolet spectrum B (UV-B) radiation counts at the site of examination. Separate comparisons were made of persons with no lens changes (n = 1,299) and persons with cortical (n = 55), nuclear (n = 104), and posterior subcapsular cataracts (n = 18). Persons with more than one type of cataract were excluded from the analysis. Cortical cataracts were associated with age (relative risk (RR) = 11.4 for age 70 years vs. age 50 years), race (RR = 3.5 for blacks vs. whites), sex (RR = 3.0 for women vs. men), educational achievement (RR = 1.8 for less than nine years of schooling vs. college), and UV-B count (RR = 3.6 for 6.0 X 10(3) counts vs. (2.6 X 10(3) counts). Nuclear cataracts were associated with age (RR = 38.6 for age 70 years vs. age 50 years), race (RR = 1.8 for black vs. white), and residence (RR = 1.6 for rural vs. urban). Posterior subcapsular cataracts were associated with diabetes (RR = 6.6 for diabetes present vs. diabetes absent) and systolic blood pressure (RR = 2.2 for 160 mmHg vs. 120 mmHg). Cortical cataracts were more common in women and more often found in locations with increased UV-B radiation counts than either nuclear or posterior subcapsular cataracts. In diabetics, the risk of posterior subcapsular cataracts was greater than the risk of nuclear cataracts (p less than 0.05) and also appeared to be greater than the risk of cortical cataracts (p = 0.06).
PDF
