Health Screening “True Positives”, “False Positives” and “Incidental Findings”: An Investigation

This report presents an investigation into the health of Queensland coal mine workers identified as having an abnormal result within the routine respiratory health screening component of the Coal Mine Workers' Health Scheme (CMWHS). The respiratory component of the health assessment includes a spirometry test, respiratory questionnaire, and chest radiograph, followed by subsequent referral to a specialist respiratory physician if abnormalities are noted.

The project focussed on understanding the health of those presenting for specialist assessment, inclusive of:

• why they were flagged as needing review
• what their lung function and medical imaging presented as
• and what their review outcome was.

This project was undertaken as the CMWHS has been significantly reformed since 2017 and this research ultimately aimed to determine whether there were any measurable differences between those workers identified as positive for a Coal Mine Dust Lung Disease (CMDLD, “true positives”) versus those who were not (“false positives” and “incidental findings”). With this information, it may be possible to garner whether the health screening program is performing adequately, or whether obvious ways to improve flagging of abnormalities during medical assessment are possible. This is of particular interest as a key challenge of health screening is the absence of discreet and unequivocal tests for CMDLD.

Ultimately, there was great overlap between the clinical parameters observed across outcome categories. No quantifiable parameter to assist in differentiating a true positive versus an incidental finding at the health screening stage could be identified. Taken together, only 6% of the individuals identified in this study were diagnosed with a CMDLD. The large majority of individuals reviewed in this study were referred for a reason of limited clinical importance, or at the very least, a reason which was not related to their occupation and could have been managed separately to the CMWHS. Within this study, hundreds of individuals were deemed “false positives” and were essentially flagged as abnormal because of issues such as an incorrect ILO grade being reported or a failure of the individual to correctly perform the spirometry test. It is this category that most obviously demonstrates the amount of unnecessary work being undertaken within the CMWHS. Further, the incidental findings category, which constituted the large majority of this study, constituted hundreds of individuals referred for abnormal results which were both predictable and explainable.

Referrals have spiked considerably since the CMWHS reform in 2017, which has placed burden on the CMWHS to run efficiently. While it was observed the proportion of true positive individuals has remained stable since this reform, the total number of referrals has grown significantly.

Two key observations as to how the CMWHS could be improved were identified in this study:

• Refining the screening process to avoid normal individuals and individuals with inconsequential or known abnormalities from requiring specialist review, and
• Adjusting what happens if one of these individuals is flagged as abnormal.

Key countermeasures to identify these cases could include those flagged with abnormal spirometry as being referred to a clinical respiratory scientist for complex lung function testing in the first instance, or those with their abnormal lung function being explained by known asthma being referred to their general practitioner.

Overall, further transparency of the workings of the CMWHS, and open discussions between key stakeholders around who is being flagged as abnormal and the clinical importance of such abnormalities, has great potential to reduce the unnecessary burden on the individuals participating in, and overseeing, the scheme.