Table 1.
Distribution of covariates among biodosimetry study subjects, mean translocation frequencies, and rate ratios by covariate categories, U.S. Radiologic Technologists Study
| Characteristic | Subjects (n = 150*) | Mean number of translocations per 100 CEs | Translocation Rate Ratios† (95% CI) |
|---|---|---|---|
| Age at blood draw‡ | |||
| 71–74 | 17 (11%) | 0.9 | 0.7 (0.5, 1.0) |
| 75–78 | 59 (39%) | 1.4 | 1.0 (referent) |
| 79–82 | 31 (21%) | 1.3 | 1.0 (0.8, 1.2) |
| 83–86 | 31 (21%) | 1.5 | 1.1 (0.9, 1.4) |
| 87–90 | 12 ( 8%) | 1.9 | 1.5 (1.1, 2.0) |
| Gender | |||
| Female | 104 (69%) | 1.2 | 1.0 (referent) |
| Male | 46 (31%) | 1.7 | 1.3 (1.1, 1.6) |
| Race | |||
| Caucasian | 147 (98%) | 1.4 | N/A |
| African American | 1 (<1%) | N/A | N/A |
| Other | 2 (1%) | N/A | N/A |
| Former cigarette smoking (number of pack years) | |||
| 0 | 87 (58%) | 1.4 | 1.0 (referent) |
| >0 – 20 | 31 (21%) | 1.2 | 1.1 (0.8, 1.5) |
| >20 – 50 | 17 (11%) | 1.5 | 1.2 (0.9, 1.6) |
| >50 | 14 ( 9%) | 1.6 | 1.7 (0.8, 3.7) |
| History of x-ray therapy for benign conditions | |||
| Never | 133 (89%) | 1.4 | 1.0 (referent) |
| Ever | 17 (11%) | 1.6 | 1.2 (0.9, 1.5) |
| In the past, allowed others to take practice x-rays | |||
| Never | 88 (59%) | 1.3 | 1.0 (referent) |
| 1 – 24 times | 35 (23%) | 1.4 | 1.0 (0.8, 1.3) |
| ≥ 25 times | 15 (10%) | 1.8 | 1.3 (1.0, 1.7) |
| Estimated occupational radiation dose to the red bone marrow§ | |||
| ≤10 mGy | 53 (35%) | 1.1 | 1.0 (referent) |
| >10 – 20 mGy | 43 (29%) | 1.3 | 1.1 (0.9, 1.5) |
| >20 – 30 mGy | 27 (18%) | 1.7 | 1.5 (1.2, 2.0) |
| >30 – 40 mGy | 17 (11%) | 1.5 | 1.4 (1.0, 1.8) |
| >40 mGy | 10 ( 7%) | 1.7 | 1.4 (1.0, 2.0) |
| Cumulative personal diagnostic red bone marrow radiation dose score** | |||
| 0 – 20 | 51 (34%) | 1.2 | 1.0 (referent) |
| >20 – 50 | 51 (34%) | 1.3 | 1.1 (0.9, 1.4) |
| >50 – 100 | 28 (17%) | 1.3 | 1.1 (0.9, 1.4) |
| >100 | 20 (13%) | 2.0 | 1.6 (1.2, 2.0) |
Abbreviations: CE-Cell equivalents; in cytogenetic studies of radiation-exposed individuals it is common to express the translocation frequency as per 100 or per 1000 CEs as this allows a comparison with other laboratories that may have painted a different combination of chromosomes. CI-Confidence Interval. N/A-Not applicable.
Does not always sum to 150 or 100% due to small numbers and percentages in the unknown category: Smoking, n=1; worked with radioisotopes, n=2; in the past allowed others to take practice x-rays, n=12.
Poisson regression adjusted for age; unknowns not included.
P-trend = <0.001 from Poisson regression with ordinal age categories treated as a continuous variable
P-trend = 0.006 from age-adjusted Poisson regression with ordinal estimated occupational red bone marrow dose categories as a continuous variable
P-trend = 0.001 from age-adjusted Poisson regression with ordinal estimated personal diagnostic red bone marrow dose score categories treated as a continuous variable. One dose score unit is approximately equivalent to 1 mGy