The APA Dictionary of Psychology defines a heuristic as follows:

In cognition, a heuristic is an experience-based strategy for solving a problem or making a decision that often provides an efficient means of finding an answer but cannot guarantee a correct outcome. By contrast, an algorithm guarantees a solution but may be much less efficient. Some heuristics, such as the availability heuristic or representativeness heuristic, involve systematic bias, also called cognitive heuristic.[1]

Because they rely on less information, heuristics are assumed to facilitate faster decision-making than strategies that require more information. Seafarers’ doctors make decisions several or many times a day and probably use a heuristic approach most of the time. An evidence-based approach often would be more time consuming, although not necessarily.

C.8.4.1 The evidence basis for medical fitness standards and criteria

The level of scientific evidence that forms the basis for decision-making regarding medical fitness criteria and their cut-off points is that of ‘expert consensus’, i.e. the lowest possible level of evidence according to Oxford centre for Evidence-based Medicine[2] [3]. Adjustments have been made throughout their 100-year history several times, taking into account the experience of practising the standards and criteria. Today we probably can conclude that the criteria and their cut-of-points are ‘sufficient’, but it probably would be hard to argue that they always are ‘necessary’.

The Guidelines on the medical examination of seafarers from ILO and IMO were developed in a series of tripartite meetings[4] between employers’ organisations, employees’ organisations and government representatives, under the leadership of ILO and IMO. Eight Government experts nominated by IMO, four ship-owner and four seafarer representatives nominated by the respective groups of the ILO’s Joint Maritime Commission attended the tripartite meetings. Several other government representations also participated, along with a number of observers from intergovernmental and non-governmental organizations[5]. The meeting reached their decision by consensus, which mean that they had to compromise. Scientific medical evidence was just one ingredient, the others being political, financial, and legal as well as party interests. It is therefore difficult to claim that it is ‘necessary’ to meet these criteria to accomplish the job tasks for a given seafarer.  We also need a definition of ‘necessary’ in this context.

However, in lack of a better option, expert consensus is the best we can get, and without compromises and consensus, there would be no international recommendations for minimum health requirements for seafarers, leaving us with a wilderness of less substantiated and less useful requirements.

Colour vision requirements[6] [7] is one example that is difficult to defend, when scrutinized. Why are there stricter requirements for seafarers serving on ships bigger than 500 GRT[8] than on ships smaller than 500 GRT in the CIE 143-2001[9]? The smaller ships usually, at least more often, are in near coastal traffic, perhaps also in littoral waters. They struggle with navigation lights ashore and on other vessels.  The waters are busier with other small boats on crossing courses. They depend on visual navigation and perception of beacon lights, lighthouses and crossing traffic in challenging waters. On the contrary, bigger ships spend most of the time at the high seas, run on autopilot systems and with no other ship in the close vicinity. Sea pilots and tugboats assist them during port calls. - It is difficult to establish a logic rationale behind the decision of the differential treatment in the CIE 143-2001, at least based on evidence.

What is the correct cut-off point for visual acuity? It was set arbitrarily, as a compromise between the three parties participating in the development of the guidelines. The revised requirements in the STCW Convention in the Manila amendments[10] were more lenient for visual acuity than the old ones, but how did they arrive to this conclusion? Again – expert consensus and political arbitration. In the end, it will be a political decision at which distance, under which light and weather conditions, a seafarer should be able to notice a shipwrecked person, debris in the water, a ship’s lanterns or rock awash. Snellen’s decimal notation requirement of 0.5 was not set based on studies demonstrating the evidence or necessity for this cut-off point.

What about testing methods used in the medical examinations? Have they been validated for the purpose? Are they objective and can another examiner reproduce them? What should be the correct cut-off points for the decision of issuing a medical certificate to someone who will also have a duty as firefighter and use a breathing device?

It seems to me that we have a long way to go, until we are able to demonstrate the ‘necessary’ cut-off point for a given position or given on-board job task. Similarly, we have a long way ahead of us until we have the validated tools we need for the assessment.

Until then – we have to use what we have: International minimum requirements, based on low evidence expert consensus.

Most medical fitness standards and criteria for occupations in other industries are national or regional, sea pilots, car drivers, and rail engine drivers. Air pilots are assessed on regional requirements based on the Convention on International Civil Aviation[11]. Together with these, the international requirements for seafarers are the only medical fitness standards that are truly international.

C.8.4.2 Evidence as a basis for the medical examiner’s daily work

Relevant cut-off points are lacking in published scientific articles considering tests used for screening for working ability. The approved doctor faces quite a challenge when trying to substantiate a decision regarding the level of risk connected to the seafarer’s health condition. The heuristic approach still is the most important.

The medical examiner is supposed to assess vision, hearing, physical and mental function, use of medicines, and the risk connected to a known medical condition, sequelae from trauma or other disabilities.

The lack of evidence regarding vision requirements is challenging on a systemic and developmental level. It is, however, easy to carry out the necessary examination of a seafarer’s vision and assess the visual acuity against the established standards and criteria. The same goes – in principle – for hearing.

Physical fitness testing is more challenging. The criteria for assessment are those recommended in the STCW Convention Part B, Table B-I/9[12].  These requirements are general in their form, describing the tasks the seafarer is supposed to carry out, the corresponding physical ability, and that the doctor should check this ability. Which tests to use, and how to conclude with “pass” or “fail” still lack detailed guidance. The evaluation is left to the doctor’s own subjective assessment, based on his experience, knowledge of work on board and knowledge of the seafarer’s condition.

The challenges are even bigger when it comes to assessment of mental fitness. No psychometric or psychological tests have so far been validated for the pre-employment testing of seafarers[13]. This does neither seem to restrain the eagerness of many developers of medical fitness criteria for seafarers to require such tests, nor medical examiners to carry them out. Nobody knows if the individuals put ashore due to failing such tests actually would not be able to serve on board, and nobody knows if the individuals passing those tests actually are fit for service. A search in PubMed, March 2019, shows a glaring emptiness regarding publications on the issue. One historical survey article by Jones and Wessely from 2003 concludes that in selection of military personnel no instrument has been identified which can accurately assess psychological vulnerability[14]. The attempts have failed, because of false-positives, false-negatives and reluctance in the target population because of stigma[15].

The IMO/ILO guidelines use the ICD-10[16] classification for medical conditions. The criteria for assessment are sometimes difficult to understand, leaving a lot to the doctor’s own discretion.

The medical examiner is supposed to give an opinion regarding the likelihood for something to happen in a period of 2 years from the date of the medical examination. The international guidelines do not, however, give guidance regarding how big a risk should be for a ‘fail’ conclusion, or what may be allowed for a ‘pass’ conclusion. It is difficult to know the likelihood for a single individual to have a recurrence, a fit, a relapse, i.e. a medical incident in the future, more so during this limited period of two years.

By searching in review databases, one sometimes can find a likelihood for different medical incidents for the group of diagnoses relevant to the seafarer. Even though this is not equal to the individual likelihood for the particular seafarer to experience an incident in the next two years’ time, it will give us an indication for further consideration. A medical record, a medical examination, supplemental evidence from hospital reports and specialist opinions are valuable supplements that form the basis for the doctor’s final decision.

C.8.4.3 From heuristics to evidence-based decision-making

Will we be able – in the future – to base our assessment on evidence? Will we be able to document the necessity of taking a specific decision through a justification based on scientific medical knowledge? In the absence of certainty, probability is the best assessment tool. The probabilistic nature of medical selection is obvious. However, is it possible to improve the accuracy of the decisions?

Today’s medical selection of seafarers is not evidence based beyond the lowest level (expert consensus).

There are many different PEME[17] schemes for seafarers, international from the UN agencies IMO and ILO, and national from the many of the more than 170 flag nations[18], usually in compliance with the international guidelines from ILO and IMO. Some guidance is given from the EU regarding medical standards, issue and registration of certificates[19] [20] and mutual recognition of seafarers’ certificates issued by member states. The different P&I Clubs[21], a number of manning agencies, ship managers and ship operators, require so-called ‘enhanced PEME’ schemes[22]. They have in common that they restrict employment opportunities more often than the IMO/ILO guidelines. They probably have a weaker evidence basis than the IMO/ILO guidelines, insofar as their group of experts are smaller, often self-appointed, and these schemes sometime give little or no guidance regarding interpretation of results, often relying on a number of laboratory tests[23], which are designed for diagnostic and therapeutic purposes, not for fitness assessment. One has to bear in mind that enhanced PEME schemes have an objective of loss prevention. This is not an objective of the statutory medical criteria. It is difficult to evaluate the enhanced PEME schemes in detail, as the criteria used for most of them are not publicly available.

From 2012, the Appellate Body of the Norwegian Maritime Authority introduced a structured approach to risk assessment in medical selection[24]. We will present the model later in this chapter.


[1] American Psychological Association: APA Dictionary of Psychology.

[2] Oxford Centre for Evidence-based Medicine – Levels of Evidence (March 2009)

[3] Burns P B, Rohrich R J, Chung K C. The Levels of Evidence and their role in Evidence-Based Medicine. Plast Reconstr Surg. 2011 Jul; 128 (1): 305-310. PMCID: PMC3124652. NIHMSID: NIHMS288127. PMID: 21701348.

[4] Joint ILO/IMO Working Group on Medical Fitness Examinations of Seafarers and Ships’ Medicine Chest

[5] Report Joint ILO–IMO Working Group on Medical Fitness Examinations of Seafarers and  Ships’ Medicine Chests. ILO/IMO/WGMG/2017/5/3 Appendix I.

[6] STCW Code Part A, Table A-I/9 with reference to CIE 143-2001.

[7] International Recommendations for Colour Vision Requirements for Transport. CIE 143-2001. ISBN 978 3 901906 09 1

[8] GRT: Gross register tonnage, a ship's total internal volume expressed in "register tons", each of which is equal to 100 cubic feet (2.83 m3)

[9] CIE 143-2001 International Recommendations for Colour Vision Requirements for Transport. ISBN:

978 3 901906 09 1

[10] Revision of the STCW Convention, 1978, adopted 25 June 2010, in force on 1 January 2012. See the IMO website: latest visited 3 April 2019.

[11] Convention on International Civil Aviation (Chicago Convention), Annex 1, Chapter 6 Medical standards.

[12] STCW Convention, Part B, Section B-I/9, Table B-I/9.

[13] Guidelines on the medical examination of seafarers, Part 3, XII, (xi), page 19. ISBN 978-92-2-127462-9 (print)

ISBN 978-92-2-127463-6 (web pdf)

[14] Jones E, Wessely S. Screening for vulnerability to psychological disorders in the military: An historical survey. Journ Med Screen 10(1):40-6 February 2003. DOI: 10.1258/096914103321610798.

[15] Jones E, Hyams KC, Wessely S. Screening for vulnerability to psychological disorders in the military: an historical survey. J Med Screen 2003;10:40-46

[16] The International Statistical Classification of Diseases and Related Health Problems (ICD), by the WHO

[17] PEME = Pre-Employment Medical Examination

[18] The IMO has 174 members and three associate members per March 2019. accessed 2019-03-26

[19] Directive 2008/106/EC of 19 November 2008 on the minimum level of training of seafarers

[20] Directive 2005/45/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 7 September 2005 on the mutual recognition of seafarers' certificates issued by the Member States and amending Directive 2001/25/EC

[21] There are 13 members of the International group of P&I Clubs accessed 2019-03-26

[22] Basurko O F. The role of manning agencies or the seafarer’s recruitment in the maritime employment market. HAL id: hal-01470405.

[23] 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.