Development of a Crosswalk to Translate Italian Occupation Codes to ISCO-68 Codes

In occupational epidemiology, job coding is an important-but time-consuming-step in assigning exposure. We implemented a tool (i.e. a crosswalk) to translate occupation codes from the Italian (ISTAT-CIP-91, n = 6319 five-digit job codes) to the International Standard Classification of Occupations (ISCO-68, n = 1881 five-digit job codes). The former is currently used in Italy for various purposes (e.g. in the National Mesothelioma Registry). The latter has been used in several studies on occupational cancers because it facilitates communication of results to the scientific community and, most importantly, because some job exposure matrices (JEMs) are based on international codes. Three authors created a table containing the crosswalk structure, providing an interpretation for each of the ISTAT-CIP-91 codes job descriptions and then manually recoding them according to ISCO-68. Two other authors independently revised it. The performance of the final version was assessed by comparison with results obtained by manual ISCO-68 coding performed in two previous case-control studies on asbestos and mesothelioma. More specifically, the automatically obtained ISCO-68 codes were merged with a JEM (DOM-JEM). The resulting individual asbestos exposure estimates (ever versus never exposed) were compared to those originally obtained (using the same DOM-JEM) from manual translation of ISTAT-CIP-91 to ISCO-68 (considered as the 'gold standard'). In the first study, among 159 peritoneal mesothelioma cases (400 job codes), Cohen's kappa was 0.91, sensitivity 0.95, and specificity 0.96. In the second study, among 716 pleural mesothelioma cases and controls (4400 job codes) kappa was 0.86, sensitivity 0.94, and specificity 0.91. Performance was better among in women. For men, performance was lower among cases than among controls (kappa 0.70, sensitivity 0.95, specificity 0.72 versus kappa 0.87, sensitivity 0.97, and specificity 0.92). In conclusion, the proposed tool allowed a rapid translation of thousands of job codes with good to excellent accuracy. The table containing ISTAT-CIP-91 codes and job descriptions and the corresponding ISCO-68 codes and job descriptions is made publicly available and can be freely used for epidemiological analyses in Italy and international collaborations.