Assessment of duration and frequency of work tasks by telephone interview:reproducibility and validity

Quantitative estimation of physical work load requires breakdown of jobs in to smaller entities. The objective was to study the inter-rater reproducibi lity of the contents, frequency and duration of work tasks assessed by tele phone interview. Two researchers interviewed 18 industrial workers with an interval of from 2 to 3 weeks in a balanced and blinded design. Altogether 114 tasks were identified, 68 of which were recorded by both interviewers. The tasks were classified into regularly occurring (n = 34) and occasional (n = 80). The outcome was the total duration of the tasks per day computed from the data on frequency and duration. Validity of the interview was stud ied against prestructured diaries filled in by nine workers. The interviewe rs' assessments of the overall contents of the tasks were rated as 'similar ' or 'very similar' for 17 of the 18 workers. Both interviewers detected al l 34 regularly occurring tasks. The intraclass correlation coefficient (ICC ) of the total duration between the interviewers was 0.81 for regularly occ urring tasks. ICCs of the total duration between the diary and the two inte rviewers were 0.90 and 0.91. However, in many cases the workers could not g ive a numerical value for duration or frequency. A telephone interview can be used as a first step in exposure assessment in epidemiological studies o n risk factors of musculoskeletal disorders. These results show that a sing le telephone interview can give reproducible and valid information of the f requency and duration of tasks occurring daily. For occasional tasks interv iew methods should be developed further.