MDD Essential Requirements

In Europe, manufacturers working under the Medical Device Directive (MDD) are given a legal "presumption of conformity" with essential requirements if they apply harmonized standards as published in the Official Journal. This feature is most often quoted as simply meaning that standards are voluntary; most people assume that essential requirements have the highest priority and must anyhow be fulfilled, in this context standards are just one way to show compliance.

Most people also assume the "presumption of conformity" only applies if the standard actually addresses the essential requirement; in other words, the presumption is not absolute. If standards don't cover an essential requirement or only provide a partial solution, the manufacturer is still obliged to provide additional solutions to ensure compliance with essential requirements.

While reasonable, this expectation is not actually supported by the directive. If the presumption was not absolute, we would need a mechanism, defined in the directive, to determine when the presumption is or is not effective. The expected mechanism would require each essential requirement to be analyzed and a formal decision made as to whether standards provide a complete solution, and if not, record the additional details necessary to provide that complete solution. The analysis would inevitably involve a characterization of the essential requirement for the individual device.

Consider for example, the application of essential requirement No. 10.1 (measurement functions) for a diagnostic ultrasound. To determine compliance we would need to compile the following information: 

  • what measurement function(s) is/are there?
  • for each measurement function, what is/are the intended purpose(s)?
  • for each measurement function, what is an appropriate accuracy for the intended purpose(s)?
  • for each measurement function, what is an appropriate test method for accuracy in design?
  • for each measurement function, what is an appropriate test method for accuracy in production?
  • for each measurement function, do the results of those test methods confirm the accuracy in design and production are suitable for the intended purpose(s)?

With this kind of detailed analysis, we can determine if standards genuinely provide a complete solution to the essential requirement, and also identify other solutions if the standards are incomplete. Given the huge range of medical devices, we know that standards struggle to provide a complete solution, and even those few that do address an essential requirement often provide only partial technical solutions which need to be supplemented with manufacturer specifications covering both design and production. Thus this analysis stage is expected to be extremely important for medical devices, and we can expect that the directive will specify exactly how to perform this analysis and what records must be maintained.

But when we look in the MDD to find what documentation must be kept (Annexes II ~ VII), we find surprisingly that there is no general requirement to document how essential requirements are fulfilled. Rather, each Annex says it is only if the manufacturer does not apply a harmonized standard that there is an obligation to document the solutions for essential requirements. This result is reinforced by Article 5, which says that member states must presume compliance with essential requirements if harmonized standards are applied. If these standards are inadequate, member states should take action to create standards, but there is no action required for the manufacturer.

Notified bodies have tried to fill this gap by insisting on an "essential requirements checklist". This checklist has now been formalized in the standard ISO/TR 16142. However, the checklist is really just a method of identifying which standards have been applied, and does not provide the analysis given above, nor record any formal decision as to whether a standard provides a complete "presumption of conformity", and if not, record the additional details necessary to provide a complete solution.  

The application of EN ISO 13485 and EN ISO 14971 were perhaps intended help to fill the gap; but there is a couple of legal problems: first is that neither of these standards, nor any management system standard actually meet the definition of a "harmonized standard" under the MDD. In principle, a harmonized standard is one that provides a complete technical solution (objective test criteria and test method), and should apply to the product, not the manufacturer (see Directive 98/34/EC, formerly 83/189/EEC).

More importantly, these standards have a key weak point: it is possible to argue under both ISO 13485 and ISO 14971 that analysis of essential requirements analysis should be performed, but there is no requirement for this analysis to be documented. Both standards limit the records to the results of the analysis, in particular ISO 14971 requires only the results of risk analysis to be recorded, not the technical analysis used to arrive at those results. While there are good reasons for this, it means that manufacturers can formally comply with these standards without ever actually documenting how essential requirements are met.

Independent observers would be somewhat bemused to find that there is no formal mechanism in the directive which forces manufacturers to document responses to important and difficult questions, such as:

  • are low cost oscillometric based NIBPs suitable for home use with high blood pressure patients?
  • are syringes with their highly variable stop/start action (stiction) suitable for use with infusion pumps when delivering critical drugs? 
  • is the accuracy of fetal weight estimation by ultrasound suitable to make clinical decisions for cesarean procedures?
  • can high powered hearing aids actually further damage hearing?

For each of the examples above, clinical literature exists showing they are real problems, yet it is rare to find these topics discussed in any detail in a manufacturer's technical file, quality system or risk management documentation, nor any formal conclusion as to whether the related essential requirement is met. The absence of such documentation is entirely in compliance with the law.

The reason for the apparent weakness in the directive can be found in the history behind the MDD. The original "new approach directives", first developed in the early 1980's were built on the assumption that published technical standards alone can reasonably assure compliance with the essential requirements, through the use of objective test methods and criteria (see 85/C 136/01 and 83/189/EEC). This is called the "general reference to standards" and requires that the standards provide " ... a guarantee of quality with regard to the essential requirements". The "general reference to standards" also says it should not be necessary to refer to "manufacturing specifications" in order to determine compliance, in other words, standards alone should provide the complete solution.

With this guarantee in place, an absolute presumption of conformity is reasonable. Manufacturers can be given a choice of either (a) applying the standard(s) and ignoring essential requirements, or (b) ignoring the standard(s) and applying essential requirements. You don't have to do both, i.e. apply standards and essential requirements. In general, essential requirements are intended to guide the standards writers, and only rarely need to be considered by those manufacturers that choose to ignore requirements in standards.  

For directives such as the LVD (low voltage), this worked well, as the standards could reasonably ensure compliance. But for other directives like the MDD, the range of devices and safety issues makes it impossible to develop comprehensive technical standards. As stated in 85/C 136/01:

"... in all areas in which the essential requirements in the public interest are such that a large number of manufacturing specifications have to be included if the public authorities are to keep intact their responsibility for protection of their citizens, the conditions for the "general reference to standards" approach are not fulfilled as this approach would have little sense"

Despite this problem, the EU went ahead and used the new approach framework for the MDD, as published in 1993. As the framework (Articles and Annexes) of CE marking directives was fixed based on Commission Decision EC COM(89) 209, the text related to the presumption of conformity and required documentation was adopted almost word for word. Thus, we can see in Annexes II ~ VII that manufacturers only need to refer to essential requirements if harmonized standards are not applied; in Article 5 the presumption of conformity is unconditional; and if there is doubt about standards assuring compliance then action is required by member states and not by manufacturers. While EC COM(89) 209 has now been updated twice (currently DECISION No 768/2008/EC), these parts of the MDD have not been yet updated to reflect the most recent framework.

So while competent authorities, notified bodies and even manufacturers might reasonably assume that the presumption of conformity is not absolute, the law doesn't support this. Moreover, the current informal approach, based on the essential requirement checklist, ISO/TR 16142, ISO 13485 and ISO 14971 also fails to effectively force manufacturers to look at each essential requirement in detail.

An interesting aside here is that the UK "transposition" of the MDD into national law includes a qualification that national standards provide a presumption of conformity with an essential requirement, "unless there are reasonable grounds for suspecting that it does not comply with that requirement". A slight problem, however, is that the UK is not allowed to do this: European law requires the local transposition to be effectively the same as the MDD, otherwise the whole concept of the common market and CE marking falls down. A secondary problem is that the UK law does not give any implementation details, such as who is authorized to decide, when such decision are required and what records are required. That the UK quietly added this modification to the MDD, despite being obviously illegal, clearly indicates the presumption of conformity is weak when applied to medical devices.   

So, is EU law at fault? Does it need to be amended to force manufacturers to analyze each essential requirement through a process of characterization, scientifically and objectively showing how the requirement is met, irrespective of standards?

Perhaps, but some caution is recommended. We need to keep in mind that CE marking may really just provide "clearance for sale", a function which needs to balance free flow of goods against risks, and which should wherever possible be based on legal certainty and objective technical specifications. Regardless of compliance with the directive, manufacturers are still liable for injury under the Product Liability Directive, which provides back up and incentive at least for serious and detectable issues. Competition also provides incentive in many other areas which are highly visible to the user, such as image quality in a diagnostic ultrasound.

Competition of course also has a darker side: pressure to reduce price and speed up market access. But, the reality is that manufacturers live in a competitive world. Like it or not, competition is a strong force and is a key reason why some of the difficult issues remain undocumented. Most manufacturers when questioned know well about these issues, but feel action is not required while the competition also takes no action. Even if we did force manufacturers to analyse essential requirements systematically, complex situations allow in bias, and the bias would tend towards keeping the status quo - it would take a lot of effort by notified bodies and regulators to detect and counter such bias working directly with each manufacturer.

In other words, forcing the analysis on manufacturers may not make much difference, and just add to compliance costs.

So, the answer here seems to be improving technical standards, forcing all manufacturers on to a "common playing field". In a round about way, Article 5 of the directive is perhaps on the best path: rather than expecting too much from manufacturers, member states should focus on creating standards that provide specific solutions (test methods and criteria) for individual medical devices.

For this to work, a critical point here is that standards committees need to take  Directive 98/34/EC seriously, creating standards that provide a complete, objective technical solutions for the product, rather than more management system standards without any specific technical details.

While we can never hope to address all safety issues in technical standards given the wide range of medical devices, it may be possible for member states to focus their efforts to those areas where product liability and competition are not effective at addressing known issues. In other words, it is not necessary for a standard to try and cover everything, just those areas which manufacturers are known to be weak.    

The main point is, the next time someone wants to discuss whether a standard provides a "presumption of conformity", make sure they have a cup of coffee ready, as the explanation will take a little time.