An Evaluation of Health Numeracy Among Radiation Therapists and Dosimetrists

Abstract

Medical events in radiation oncology often involve error pathways related to practitioners’ grasp of numeracy. Numeracy has been shown to be problematic among physicians, medical students, nurses, and pharmacists, but has not been assessed in radiation therapists or dosimetrists. We herein assess numeracy and subjective opinions about the expression of dose in a series of radiation therapists and dosimetrists. An existing 20-question survey of health numeracy, the Numeracy Understanding for Medicine instrument (NUMI) was adapted for radiation therapists and dosimetrists. Questions included basic demographics, preferences for dose units (cGy vs. Gy) and associated vulnerability to error. Health numeracy scores were categorized as follows: “low” (0-7), “low average” (8-12), “high average” (13-17), or “high” (18-20). Spearman’s rho, Student’s t-test and chi-square were used for comparisons between different groups. MANOVA was used to compare performances for dose units. The American Society of Radiologic Technologists (ASRT) sent out an email invitation to 14,228 radiation oncology member addressees. 848 individuals accessed the survey (response rate=6%). Of these, 79% were eligible for scoring. 66% identified as therapists, and 25% identified as dosimetrists, and 9% identified as other. Respondents were 25% male and 75% female, consistent with ASRT membership statistics. Mean NUMI score for those with some college education is 11.3, and with at least 4 years of college the mean score is 16.4. Overall in this sample, 1% scored “low-average”, 36% “high-average” and 63% scored “high” (median score 18). Health numeracy score was inversely correlated with older age (Spearman’s rho -0.17, p<.001) and length of time in practice (Spearman’s rho -0.18, p<.001). Men had a significantly higher mean score than women (18.04 and 17.32, p<0.001). No significant difference in health numeracy score was detected between therapists and dosimetrists (p=0.34). The unit cGy was preferred by 64% of those surveyed, Gy was preferred by 13% of those surveyed, and no preference or a variable preference was stated by 23%. Subjectively, 72% of respondents felt that cGy and Gy did not differ in error susceptibility, 25% believed Gy was more susceptible to error, and 3% felt cGy would be more error prone. There were no differences in the results for questions that were repeated using cGy vs Gy. Although limited by non-response bias, ASRT members’ numeracy compares favorably to the values reported in the general population. No significant difference in performance was seen between cGy or Gy although the cGy unit was preferred. Younger age, less time in practice, and male gender were significantly associated with higher health numeracy, while occupation was not.