Reply to 'Big data, selection bias and clinical significance
Julie Crewe, Research fellow, Lions Eye Institute, Centre for Ophthalmology and Vision Science, University of Western Australia, Australia.
Tim Threlfall, Research Fellow, Western Australian Cancer Registry, Department of Health, Western Australia, Australia
Antony Clark, Consultant Ophatlmologist, Lions Eye Institute, Centre for Ophthalmology and Vision Science, University of Western Australia, Australia.
Paul Sanfilippo, Research Fellow, Centre for Eye Research Australia, University of Melbourne, Royal Victorian Eye and Ear Hospital, Melbourne, Australia.
David Mackey, Consultant Ophthalmologist/Director, Lions Eye Institute, Centre for Ophthalmology and Vision Science, University of Western Australia, Australia.
Other Contributors:
Antony Clark
Paul Sanfilippo
David Mackey
March 23, 2018
Conflict of Interest
None declared
We thank the authors for their comments and insights on our paper ‘Pterygia are indicators of an increased risk of developing cutaneous melanomas’.
We agree that there was selection bias within the pterygium cases. All cases were identified as hospital in-patients and therefore represent that small select portion of the population who were receiving treatment for (or removal of) their pterygium. We made no assumptions about whether these cases were more or less severe than untreated pterygia or whether the removals were performed for cosmetic or other reasons. The strengths of this study are that it included all in-hospital cases treated in Western Australia over a 30 year time period, without prejudice.
While melanoma is an uncommon problem in China, it is a major health issue in Australia and New Zealand. The clinical relevance of this study should be viewed against the background of the world’s highest incidence rates of cutaneous melanoma that currently exist, with up to 60 cases per 100,000 population1-3 in Australia and New Zealand. Contrast this with the incidence rates of East Asian countries of approximately 0.7 cases per 100,000 population.4 Both non-melanoma and melanoma skin cancers are a major health priority for cancer prevention research. We are not suggesting that pterygium be used as the sole indicator for a population wide screening program. There are well established major screening and surveillance programs in place in Australia. Our study adds a new variable to the calculation of risk for individuals (along with skin colour, hair colour, latitude and sun exposure). We do not believe our findings will cause increased anxiety to people who develop pterygium but will be a useful aid to increasing awareness of the health risks associated with high levels of solar radiation that are a part of life in Australia.
Table 5 age groups are correct as shown but could also be written as: <50 (aged 0 to 49.99) years and ≥50 (aged 50 or more) years.
The suggested correction (>50 years and <49 years) would exclude all people aged 50 years which would be incorrect for the data shown.
Julie Crewe
Tim Threlfall
Antony Clark
Paul Sanfilippo
Professor David Mackey
References
1 MacLennan R, Green AC, McLeod GRC, Martin NG. Increasing Incidence of Cutaneous Melanoma in Queensland, Australia. JNCI: Journal of the National Cancer Institute. 1992;84(18):1427-32 DOI:10.1093/jnci/84.18.1427
2 Marks R. The Changing Incidence and Mortality of Melanoma in Australia. In: Dummer R, Nestle FO, Burg G, editors. Cancers of the Skin: Proceedings of the 8th World Congress. Berlin, Heidelberg: Springer Berlin Heidelberg; 2002. p. 113-21.
3 Garbe C, Leiter U. Melanoma epidemiology and trends. Clinics in Dermatology. 2009;27(1):3-9 https://doi.org/10.1016/j.clindermatol.2008.09.001
4 Makredes M, Hui SK, Kimball AB. Melanoma in Hong Kong between 1983 and 2002: a decreasing trend in incidence observed in a complex socio–political and economic setting. Melanoma Research. 2010;20(5):427-30 DOI:10.1097/CMR.0b013e3283281072