Abstract
Imagine you go to your favorite health care provider seeking help for chronic, increasing pain. Your provider starts a large apparatus of examinations, takes blood samples, X-rays your spine and joints, and—since he or she is probably a complementary medicine practitioner with a whole health approach—even measures heart rate variability and salivary cortisol. A week later, the results are available, all values are within the norms, and the delighted provider released you as perfectly healthy. Despite severe pain, which is however not objectively measurable and you thus don't know whether it exists anyway.
Absurd? I hope so. At least in health care. In clinical research, on the other hand, there seems to be a strong aversion to measuring things for what they are. So pain or stress by asking patients about their pain or stress. Instead, complicated “digital biomarkers” are constructed, as patients are obviously not in a position to assess something as complex as pain subjectively and it also seems to take an insane amount of time to do so: 1 after all, a cross on a numerical rating scale takes up to 1–2 sec.
For many decades, there has been a deep mistrust of patients' self-awareness, and they have been denied the ability to assess their own situation. Patient-reported outcomes and patient-reported outcome measures (PROMs) are accordingly a rather recent phenomenon that still meets with mistrust in the population. The whole thing goes so far that even patients prefer “objective” performance measures to PROMS. 2 At the same time, simplicity has always been a good guideline in research. Occam's razor, that is, the demand to always to prefer the simplest of various possible theories and to leave out unnecessary hypotheses (today, perhaps better known as KISS—Keep it simple, stupid!), can also be applied to outcome measures. Why develop complicated objective measures for pain or stress? Quantitative sensory testing or the cortisols awakening response are of course justified in research into pathomechanisms or effect mechanisms. However, if I want to know whether someone is experiencing increased or decreased pain or stress, it is probably easier to ask about it.
And while relying on subjective measures can still cause astonishment, disappointment, or rejection in discussions outside clinical research, PROMs are now firmly established in clinical research. There are hundreds of validated PROMs, some of which have been used for decades. 3 PROMs are always useful when subjectivity is at the core of the target parameter, that is, when the symptom to be measured is subjective in itself and cannot be objectified without frictional losses, such as pain or stress, but also quality of life, well-being, or happiness. Hypertension, heart attacks, or tumor growth naturally remain central in studies that address these parameters.
Patient-reported outcomes are defined as “any report of the status of a patient's health condition that comes directly from the patient, without interpretation of the patient's response by a clinician or anyone else.” 4
Numerous evidence-based recommendations for PROMs in specific patient groups are available today. For example, the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) defined six core domains for clinical trials on chronic pain already 20 years ago: pain, physical functioning, emotional functioning, improvement, and satisfaction with treatment, adverse events, and participant disposition; 5 and provides various PROMs to measure them. Physician-reported or objectively measured parameters should only be used in exceptional cases when the patient is unable to express themselves. 6
Too unspecific? No problem: for example, in rheumatology, the Outcome Measures in Rheumatology (OMERACT) collaboration 7 provides more specific target parameters. Depending on the specific disease, objective measures also play a role here; however, the subjective experience is of course reported by the patient and is the main focus if the symptoms of a disease are predominantly subjective. For fibromyalgia, for example, domains were defined that should be assessed with graded priority: pain, tenderness, fatigue, patient global health, multidimensional function, and sleep disturbance should be assessed in all clinical trials, objective markers such as cerebrospinal fluid biomarkers and functional imaging are at most additional measures. 8,9
Although it is not entirely clear whether PROMs also improve care, there is preliminary evidence that they do: if cancer patients can spontaneously provide standardized self-report when they experience symptoms, they are treated more frequently, show a higher quality of life than if they have to rely on the treating physician's report. 10 In the long term, there even seems to be a survival advantage when patients are given back the power to interpret their condition themselves.
Why am I writing this, which seems perfectly clear and logical? I recently had a conversation with a colleague who planned a clinical trial on fibromyalgia and was still unsure whether to choose central sensitization or autonomous regulation as the primary outcome. It therefore seems useful to point this out from time to time: when we want to know how a patient is doing, the real expert is usually sitting in front of us and not next door in the lab.