CLUE I & II Studies

Lead Contact and/or Principal Investigator (PI):

  • Kala Visvanathan, M.B.B.S., F.R.A.C.P., M.H.S.
    Bloomberg School of Public Health
    Johns Hopkins University

Funded Since: 1974
Funding Source: Johns Hopkins University Bloomberg School of Public Health and NCI Intramural Program
Year(s) of Enrollment: 1974 (CLUE I) & 1989 (CLUE II)
Study Website: Web Site Policy

CLUE I - Campaign Against Cancer and Stroke

From August through November 1974, the Campaign against Cancer and Stroke was conducted in Washington County, MD. Referred to as CLUE I (from the slogan "Give us a Clue to Cancer"), the study was designed to collect blood samples from as many adults as possible to provide specimens for a serum bank. Mobile trailers were stationed in a wide variety of locations in an effort to give all segments of the community ample opportunity to participate. A total of 25,802 persons donated blood, of whom 20,305 were county residents. Linkage of the records from this program to those of a private census in the summer of 1975 indicated that almost one third of the adult population of the county had participated. Participation was best in the age group 35 to 65 years, and was slightly better among females, the better-educated, and nonsmokers. A brief medical history form was completed at the time of blood collection. A medication history (including use of vitamins and hormones) and blood pressure were taken. Blood was drawn into 15 ml Vacutainers, allowed to clot, refrigerated until it was centrifuged, and two 6 ml aliquots of serum were removed for storage at -70°C. The time from blood draw to freezing was usually only a few hours, and never more than 24 hours.

CLUE II - Campaign Against Cancer and Heart Disease

CLUE II was similar to CLUE I in most respects. It was conducted from May through October 1989. Similar mobile trailers were used that operated in all areas of the county and at all times of day except between 1 and 6 a.m. Brief medical histories and blood pressure readings were taken, and 20 ml of blood was drawn into heparinized Vacutainers. Specimens were refrigerated at once, and processed within 24 hours. Plasma, buffy coat, and red blood cells have been preserved at -70°C. Participants were given a food frequency questionnaire to complete at home and asked to return it with a toenail clipping for trace metal assays. Cholesterol results were mailed to participants within a few days of blood draw, along with guidelines for physician referral. A total of 32,898 persons participated, of whom 25,081 gave Washington County addresses. Comparisons with published figures from the 1990 Census indicated that again approximately 30 percent of adult residents had participated. As before, women and the better educated had higher than average participation rates, as did the age group 45 to 70 years. Forty-one percent of the Washington County residents who participated in CLUE I (n= 8,395) also participated in CLUE II. Information has been collected from this cohort as far back as 1963 and as recently as 1998 from the following sources: private censuses conducted in 1963 and 1975, questionnaires completed at the times of blood donation in 1974 and 1989 and follow-up information from questionnaires administered in 1996, 1998, 2000, 2003, and 2005.

Among the CLUE I participants, 2,659 cases of cancer have developed with serum remaining from 89 percent (2,375) of cases. Cancer has developed in 895 CLUE II participants, and plasma remains for 96 percent (858) of these cases.


For CLUE I and II, data also were obtained on age, race, sex, marital status, time since last menstrual period, smoking history, blood pressure, medication use, hormone use, height and weight currently and at age 21 (CLUE II only), and from a food-frequency questionnaire (CLUE II only).

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