ALF MAGNE HORNELAND
We have touched upon the issue of using additional laboratory tests for screening purposes in the pre-employment medical examination of seafarers. We will have a closer look at that specific question, without going too much into detail.
In some PEME schemes, tests are required only on a medical indication[1]. Other schemes require a diversity of laboratory tests as a screen for disease or pre-disease states[2].
Most, if not all, such tests are developed for diagnostic purposes, which means that they are suitable for use upon indication but have a much lower positive predictive value used for screening, where we do not have such an indication and in a population where prevalence for many medical conditions is low.
The cut-off points in quantitative or semi-quantitative tests, which are suitable for therapeutic purposes, are not necessarily suitable for a decision on medical selection questions. The level of blood pressure that indicates treatment for hypertension is different from the level of blood pressure that make you expect an incident to come within the validity period of the medical certificate.
Some tests are more or less irrelevant if used for ruling in or ruling out of work at sea. One obvious example is a HIV-test. It simply can tell little or nothing regarding working capacity or likelihood for medical incidents in the validity period. Used this way, this is a clear violation of international antidiscrimination agreements and national antidiscrimination legislation of many countries. Today HIV positive individuals can live a normal life without having a risk of complications within the validity period of a seafarer medical certificate, provided there is necessary treatment and follow-up, and the approved doctor has confirmed this. In addition, the importance of precautions to prevent transmission the infection to others must be emphasised[3] [4].
Horneland and Stannard recommended a model for assessment of the suitability of such tests in their article (2017)[5]:
Step | Description |
1 | Identification of disease with the likelihood of unacceptable risk to ship, crew and self – and which can be identified by a specific test · Which medical incidents could the disease lead to · What is the likely incidence (per year) for such incidents given established diagnosis |
2 | Which test is considered to screen asymptomatic individuals? |
3 | Which mitigating measures can a positive test result lead to? |
4 | Is the test considered capable of detecting the disease at an asymptomatic stage? · Consider the appropriate statistical parameters |
5 | Is the test safe? |
6 | Is the test cost effective? · Are potential savings greater than the likely costs to be incurred without the test? · Calculate number needed to test to avoid one medical incident over the next 2 years |
7 | Is the test available to all seafarers internationally without need for further referral? |
8 | Can use of the test lead to a demonstrable improvement in risk assessment? |
9 | CONCLUSION: Is the screening test appropriate to manage risk to an acceptable level? |
Table 7. Suggested decision aid for the assessment of the appropriateness of biochemical tests and imaging techniques in pre-employment medical examinations (PEME) (Horneland&Stannard 2017) | |
This approach is a list of questions that should be answered before a test is included in a screening programme.
[1] Regulations of 5 June 2014 No. 805 on medical examination of employees on Norwegian ships and mobile offshore units
[2] Horneland AM, Stannard SL. Decision aid for the use of additional tests during the pre-employment medical examination (PEME) of seafarers. Int Marit Health. 2017;68(2):90-98. doi: 10.5603/IMH.2017.0017. PMID 28660611.
[3] Cohen MS. Successful treatment of HIV eliminates sexual transmission. Lancet. 2019-05-02. DOI: https://doi.org./10.1016/S0140-6736(19)30701-9.
[4] Cohen MS, Chen YQ, McCauley M et al. Prevention of HIV-1 infection with early antiretroviral therapy. N Engl J Med.2011;365:493-505
[5] Horneland AM, Stannard SL. Decision aid for the use of additional tests during the pre-employment medical examination (PEME) of seafarers. Int Marit Health. 2017;68(2):90-98. doi: 10.5603/IMH.2017.0017. PMID 28660611.