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Table 1.

Distribution of covariates among biodosimetry study subjects, mean translocation frequencies, and rate ratios by covariate categories, U.S. Radiologic Technologists Study

CharacteristicSubjects (n = 150)*Mean number of translocations per 100 CEsTranslocation rate ratios (95% CI)
Age at blood draw (y)    
    71–74 17 (11%) 0.9 0.7 (0.5, 1.0) 
    75–78 59 (39%) 1.4 1.0 (reference) 
    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 (reference) 
    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 (reference) 
    >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 (reference) 
    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 (reference) 
    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 RBM§    
    ≤10 mGy 53 (35%) 1.1 1.0 (reference) 
    >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 RBM radiation dose score    
    0–20 51 (34%) 1.2 1.0 (reference) 
    >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) 
CharacteristicSubjects (n = 150)*Mean number of translocations per 100 CEsTranslocation rate ratios (95% CI)
Age at blood draw (y)    
    71–74 17 (11%) 0.9 0.7 (0.5, 1.0) 
    75–78 59 (39%) 1.4 1.0 (reference) 
    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 (reference) 
    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 (reference) 
    >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 (reference) 
    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 (reference) 
    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 RBM§    
    ≤10 mGy 53 (35%) 1.1 1.0 (reference) 
    >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 RBM radiation dose score    
    0–20 51 (34%) 1.2 1.0 (reference) 
    >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) 

NOTE: In cytogenetic studies of radiation-exposed individuals, it is common to express the translocation frequency as per 100 or per 1,000 CEs as this allows a comparison with other laboratories that may have painted a different combination of chromosomes.

Abbreviation: 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.

Ptrend = <0.001 from Poisson regression with ordinal age categories treated as a continuous variable.

§

Ptrend = 0.006 from age-adjusted Poisson regression with ordinal estimated occupational RBM dose categories as a continuous variable.

Ptrend = 0.001 from age-adjusted Poisson regression with ordinal estimated personal diagnostic RBM dose score categories treated as a continuous variable. One dose score unit is approximately equivalent to 1 mGy.

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