A diagnosis that turns out afterwards to be incorrect is not automatically a medical error. The assessment looks at what the doctor at the moment of treatment knew and could know, and at what a reasonably competent professional colleague would have done in that situation.
Written by Onur Arslan, lawyer at Arslan Advocaten. Registered in the areas-of-law register of the Netherlands Bar for employment law and personal injury. Last updated: 17 September 2026.
That distinction — between what we know now and what could reasonably be expected then — determines virtually every case.
When is a diagnostic error culpable?
The standard is set out in article 7:453 of the Dutch Civil Code: in their work the care provider must observe the care of a good care provider, in accordance with the professional standard and the applicable quality standards. That is an obligation to use best efforts, not a guarantee of a correct diagnosis.
Do not test it afterwards with today’s knowledge. If it turns out months later that a serious condition was at play, that in itself does not prove that the earlier diagnosis was wrong. The question is whether the doctor, with the symptoms and data that existed at the time, arrived at a responsible assessment.
| Points rather to a responsible assessment | Points rather to a breach of the standard |
|---|---|
| The symptoms fitted the diagnosis made and the differential diagnosis was considered | Alarm symptoms were not recognised or not followed up, while the guideline required that |
| The examination indicated by the guideline was carried out, or there was a reasoned departure from it | Necessary follow-up examination was not requested without a reason for that being recorded |
| A follow-up appointment was made with a clear instruction about when to come back | With persistent or worsening symptoms there was no reconsideration and no referral |
| The result was assessed and discussed with you, and that was recorded | A result was overlooked, not fed back or not followed up |
Whether there was a departure from the standard is a clinical question. It is answered by an expert from the same field, on the basis of your file. We do not give a medical opinion at a distance; what we do is assess which data are needed and have them tested.
Examples: where things go wrong in practice
The situations below are types of error that recur in case files and disciplinary cases, not cases of our firm and not medical statements about your situation. They have deliberately been described at the level of the process, because that is usually where a diagnostic error becomes demonstrable: not because a doctor saw something wrongly, but because a step in the pathway was not taken or not recorded. That is also the legal point of attack, because article 7:453 of the Civil Code requires the care of a good care provider in accordance with the professional standard, and article 7:454 of the Civil Code imposes a duty to keep a file.
| What happens | Why this is legally relevant | What you request |
|---|---|---|
| A result comes in but is not reported back. Blood tests or imaging show something, but nobody calls and no follow-up action is taken | This is not about the assessment itself but about the follow-up. An abnormal result that goes unseen is a gap in the process that is independent of the question whether the first diagnosis was defensible | The date and time of the result, who viewed it, and what note about it is in the file |
| Persistent complaints do not lead to reconsideration. You come back three or four times with the same complaint and receive the same advice every time | The professional standard calls for reconsideration where the course of the illness does not fit the diagnosis given. Repeat contacts without a visible change of direction are therefore a central question | All contact moments with the date and the complaint described, so that the pattern becomes visible |
| The handover between practitioners or services is incomplete. Information is lost at a change of shift, a referral or a transfer | Here there is often no single practitioner individually at fault, while the chain as a whole falls short. That makes the question of whom you address more important than the question of who got it wrong | Handover messages, referral letters and the time at which the receiving party got the information |
| Indicated investigation is not carried out, without a recorded reason. The guideline indicates investigation for this pattern of complaints, and it does not happen | Departing from a guideline is permitted, but it must then be apparent why. If that reasoning is missing from the file, that weakens the care provider’s position | The guideline or protocol followed, and the file note in which the consideration is set out |
| An alarm symptom is not recognised as such. There is a phenomenon that, according to the standard, calls for immediate action | This is the most serious category, because the standard leaves the least room here. It must, however, be established that the symptom was reported and documented at the time | Your own notes about what you reported and when, alongside what has been recorded in the file |
What these examples have in common. In all five cases the question is not whether the doctor was wrong, but whether the pathway met what could be expected of a reasonably acting and reasonably competent colleague. That is why your file weighs so heavily, and why a missing note is often more important than one that is there.
A practical point in older cases. Article 7:454(3) of the Civil Code obliges the care provider to keep the file for twenty years, counted from the last change made to it, or longer if the care of a good care provider so requires. If your situation goes back years, request the file all the same; the fact that it was a long time ago does not mean the documents are gone. Do watch the limitation period, though, which follows a clock of its own.
The timeline: the most important document in your file
With a diagnostic error everything turns on the sequence of events. So first put this on paper, with dates:
- Symptoms: when did they start, and how did they develop?
- Consultations: which dates, with which doctor, what did you report and what was said?
- Examination: which examination was requested, when was it carried out, and when was the result known?
- Feedback: when and how was that result discussed with you?
- Referral: when was a referral made, and on whose initiative?
- The correct diagnosis: when was it made and by whom?
- Consequences: what treatment was needed after that, and what could it have been earlier?
In addition, request your medical file. Under article 7:454 of the Civil Code the care provider must set up a file containing the health data and the procedures carried out, and you are entitled to inspection and a copy. Expressly ask for imaging, laboratory results and the records of the consultations as well.
Keeping two kinds of loss apart
This is the point at which many claims fail. Your condition already existed; it was not caused by the doctor. What qualifies for compensation is solely the avoidable additional loss caused by the delay or the incorrect assessment.
| Loss caused by the condition itself | Avoidable additional loss |
|---|---|
| Consequences that would also have occurred with a timely, correct diagnosis | Consequences that would not have occurred, or would have been milder, with timely intervention |
| Does not qualify for compensation | This is what the claim focuses on |
| Example: a treatment that was needed in any event | Example: a heavier procedure that became necessary because of the delay, longer absence, an extra period of recovery |
So the key question is always: what would have happened with timely and correct conduct? That calls for a medical opinion about the likely course of events, the so-called hypothetical course.
Where the causal connection is uncertain
With diagnostic errors it is often impossible to establish with certainty how things would have gone. The law has two different doctrines for that, and they are regularly mixed up.
| Loss of a chance | Proportional liability | |
|---|---|---|
| Where the uncertainty lies | It is established that a chance has been taken away; what is uncertain is how large the loss is | It is uncertain whether the breach of the standard caused the loss, alongside other possible causes |
| What is compensated | The value of the lost chance of a better outcome | Part of the loss, to the extent to which the breach of the standard may have contributed to it |
| Application | Need not be applied with the same restraint | With restraint, because there is a risk that someone becomes liable for loss they did not cause, or did not cause to that extent |
There is no automatic percentage formula. Anyone who claims that a missed diagnosis "therefore" produces a fixed percentage of the loss disregards the assessment that must be made in each case, on the basis of an expert opinion about the likely course of events. Which doctrine is at issue and with what outcome depends entirely on the facts of your file.
Evidence: who must prove what?
The main rule in article 150 of the Code of Civil Procedure is that you set out, and where it is disputed prove, the breach of the standard, the loss and the causal connection. There is no general reversal of the burden of proof in medical cases.
What there is, is an enhanced duty to set out the facts on the part of the care provider: it is required to provide sufficient factual data to substantiate your assertions and thereby give starting points for evidence. That is connected with its duty to keep a file under article 7:454 of the Civil Code. If the file is incomplete, if the record of a consultation is missing or if it is not recorded why there was a departure from a guideline, that can work to its disadvantage. It does not produce liability automatically.
Who you address depends on the setting. Where the procedures took place in a hospital that is not a party to the treatment contract, that hospital is jointly liable for a shortcoming under article 7:462 of the Civil Code, as if it were itself a party. That liability cannot be limited or excluded under article 7:463 of the Civil Code.
How we assess it, and what it costs
We start with your timeline and the medical file. After that we assess whether there is reason to instruct a medical expert, and if so from which field and with which terms of reference. Those terms of reference are decisive: they contain the question about the hypothetical course of events with timely and correct conduct.
We make a written arrangement about the costs in advance, so that you know what an assessment and any follow-up cost. Where liability is admitted, the reasonable costs of legal assistance are in principle borne by the liable party under article 6:96 of the Civil Code; whether that works out that way in your case depends on the admission and the extent of the loss, and we cannot promise it in advance. If you have legal expenses insurance, check your cover first.
Period
With loss caused by injury your claim becomes time-barred under article 3:310(5) of the Civil Code on the expiry of five years after the day following the one on which you became aware of both the loss and the person liable. No absolute period of twenty years applies, provided the event took place on or after 1 February 2004. How you interrupt the limitation period is set out in limitation in medical liability cases.
If it concerns a medication or dosage error, see the wrong medication or a dosage error. With dental treatment, see medical error at the dentist or oral surgeon. Specifically about liability and compensation with diagnostic errors you can read more in wrong diagnosis: liability and compensation.
Would you like to have your file assessed? Contact us without obligation and keep your timeline and medical documents to hand.
Frequently asked questions
Is an incorrect diagnosis automatically a medical error?
No. Article 7:453 of the Civil Code requires the care provider to observe the care of a good care provider in accordance with the professional standard; that is an obligation to use best efforts and not a guarantee of a correct diagnosis. The assessment looks at what the doctor knew and could know at the moment of treatment. That a different condition turns out afterwards to be at play proves nothing in itself. There is only a breach of the standard where, for instance, alarm symptoms were not followed up, necessary examination was omitted without a recorded reason, or there was no reconsideration and referral with persistent symptoms.
Which loss qualifies for compensation?
Only the avoidable additional loss, that is to say the consequences that would not have occurred, or would have been milder, with timely and correct conduct. The consequences of the underlying condition itself do not qualify for compensation; they were not caused by the doctor. The key question is therefore always what would have happened with a timely, correct diagnosis, the so-called hypothetical course of events. That calls for a medical opinion and is usually the most difficult part of the case with diagnostic errors.
What is loss of a chance, and does a fixed percentage apply to it?
Loss of a chance concerns the situation in which it is established, under the ordinary rules of evidence, that the error took away from you a real chance of a better outcome, while it remains uncertain whether that chance would have materialised; what is compensated is then the value of that lost chance. That is something different from proportional liability, where it is precisely uncertain whether the breach of the standard caused the loss alongside other possible causes; that latter doctrine must be applied with restraint, because otherwise someone can become liable for loss they did not cause. There is no automatic percentage formula: which doctrine applies and with what outcome depends on the facts and on an expert opinion.
Does the burden of proof lie with me or with the doctor?
In principle with you: under article 150 of the Code of Civil Procedure you must set out, and where it is disputed prove, the breach of the standard, the loss and the causal connection. There is no general reversal of the burden of proof in medical cases. There is, however, an enhanced duty on the care provider to set out the facts: it must provide sufficient factual data to substantiate your assertions, which is connected with its duty to keep a file under article 7:454 of the Civil Code. If the record of a consultation is missing, or if it is not recorded why there was a departure from a guideline, that can work to its disadvantage, but it does not produce liability automatically.
Does a condition found later prove that an error was made earlier?
No. The assessment looks at what the doctor knew and could reasonably know at the moment of treatment, measured against the professional standard as it then was. That a different condition comes to light afterwards does not in itself mean that the earlier assessment was careless. There is only a breach of the standard where, for instance, alarm symptoms were not followed up, the examination indicated by the guideline was omitted without a recorded reason, a result was not followed up, or there was no reconsideration and referral with persistent symptoms.
What additional loss can be connected with the delay?
Only the loss that would not have occurred, or would have been milder, with timely and correct conduct. Think of a heavier procedure that became necessary because of the delay, a longer period of recovery, extra medical costs and the deductible, income lost during a longer absence and, with permanent injury, future loss as well, domestic help, travel costs and compensation for pain and suffering for the extra suffering. The consequences of the underlying condition itself do not qualify for compensation; they were not caused by the doctor. So the key question remains what would have happened with a timely diagnosis.
What are examples of a medical error in the case of a wrong diagnosis?
In practice it is usually not about a doctor who saw something wrongly, but about a step in the process that was not taken or not recorded. Five situations keep recurring: a result that comes in but is not reported back, persistent complaints that do not lead to reconsideration of the diagnosis, an incomplete handover between practitioners or services, indicated investigation that is not carried out without a recorded reason, and an alarm symptom that is not recognised as such. In all five cases the legal question is not whether the doctor was wrong, but whether the pathway met what could be expected of a reasonably acting and reasonably competent colleague, as article 7:453 of the Civil Code prescribes. These are general examples by way of explanation and not cases of our firm.
