Types of measures
discriminative
A discriminative measure tries to maximally discriminate between a ‘patient’ group and a ‘healthy control’ group, or two ‘patient’ groups (for example, within a triage process) at one point in time.
evaluative
An evaluative outcome measure focuses on capturing clinical changes over time.
predictive
A predictive measure can be utilised to infer the likelihood of a particular outcome occurring in the future.
Other terms
absenteeism
Unexcused and unscheduled absence from duty by an employee. In the context of occupational health and safety in the workplace, absenteeism is the absence or habitual absences of an employee from their workplace without legitimate causes or excuse. Legitimate causes for absenteeism include personal illness and family issues. Unexcused absenteeism can be caused by factors such as poor work environment, lack of commitment by the employee to their job, mental health issues such as depression or marital problems, or substance abuse. See presenteeism.
catastrophising
Refers to a negative cognitive-affective response to anticipated or actual pain. Catastrophising is an exaggerated and negative cognitive and emotional response during an actual or anticipated painful stimulation. Catastrophising is often characterised by people magnifying their feelings about painful situations and ruminating about them, which can combine with feelings of helplessness. Catastrophising plays an important role in models of pain chronicity, showing a high correlation with both pain intensity and disability.
Access information on catastrophising in an overview of the psychological basis of pain by Physiopedia.
clinical prediction rule
A mathematical tool intended to guide clinicians in their everyday decision making. Ideally, a reliable predictive factor or model would combine both a high sensitivity with a high specificity. In other words, it would correctly identify as high a proportion as possible of the patients fated to have the outcome in question (sensitivity) while excluding those who will not have the outcome (specificity).
Access information in an article published by the BMJ.
clinimetrics
Refers to a methodologic discipline that focuses on the quality and utility of clinical measurements. The clinimetric properties of an outcome measure are not fixed but vary among different settings and populations in which the outcome measure is used. The clinimetric properties of outcome measures include both psychometric aspects (validity, reliability and responsiveness) and clinical utility (feasibility, interpretability and external validity).
ePPOC
Electronic Persistent Pain Outcomes Collaboration.
Access information from the Australian Health Services Research Institute at the University of Wollongong.
fear avoidance
When a person misinterprets pain in a catastrophising way, this can lead to pain-related fear and associated safety-seeking behaviours, such as avoidance. Outcomes of fear-avoidance behaviour can include disuse and disability and, in turn, a lowering of the threshold at which the person will experience pain.
Access information on the fear avoidance model by Physiopedia.
floor effect, ceiling effect
Scale width, or the capacity of a scale to have initial scores that are able to demonstrate change over time, is an important aspect of the interpretability of an outcome measure. Scale width encompasses the concepts of floor and ceiling effects. A floor effect occurs when a patient scores so low on an outcome measure that further deterioration cannot be measured. Ceiling effects occur when a patient scores so high on an outcome measure that improvement cannot be measured. Interpretability of outcome measures is therefore compromised when floor and ceiling effects occur (Daly, 2010).
IMMPACT
Initiative on Methods, Measurement and Pain Assessment in Clinical Trials.
Access information on the IMMPACT website.
kinesiophobia
An excessive, irrational and debilitating fear of movement and activity resulting from a feeling of vulnerability to painful injury or reinjury.
Access information in an overview of the psychological basis of pain by Physiopedia.
minimum clinically important difference (MCID)
The smallest change in outcome measure score that an individual perceives as important. This value may be affected by many factors such as who determines the MCID, for example, a patient, a clinician or a third party; the cost of the intervention being measured; the risk and the extent of an adverse event that may occur with an intervention and also the level and context of the patient’s disability or pain intensity. MCID can measure deterioration as well as improvement, but it should not be assumed that the absolute value of these changes is equal, as a small deterioration can be of greater or lesser importance to the patient than a small improvement and vice versa. An approximation, from a systematic review of studies of chronic pain, suggests that the MCID is close to half a standard deviation or one point on a seven point scale. The results from a number of studies on different types of pain have demonstrated that the baseline entry score has an effect on the MCID.
It is important to recognise that the MCID measures a different construct to the MDC. Together they provide an interpretation of the statistical and clinical importance of a change in score on an outcome measure. If the MCID is smaller than the MDC it can be concluded that the outcome measure cannot reliably measure MCID (Daly, 2010).
MDC, MDC90, MDC95
Minimum detectable change (MDC) utilises a statistically derived distribution based approach to determine the magnitude of change in score required to be certain that a change is greater than that expected due to error alone. The MDC is a statistical distribution of the margins of error based on the standard error of measurement (SEM) which can be altered to reflect different confidence intervals. Some researchers report the MDC90 which can be interpreted as meaning that 90% of stable patients, i.e patients that are not changing, are likely to display a retest less than the value of the MDC90. Others determine the MDC95 to correspond with the 95% confidence interval.
It is important to recognise that the MDC measures a different construct to the MCID. Together they provide an interpretation of the statistical and clinical importance of a change in score on an outcome measure. If the MCID is smaller than the MDC it can be concluded that the outcome measure cannot reliably measure MCID (Daly, 2010).
neuropathic pain
Pain caused by a lesion or disease of the somatosensory nervous system. Neuropathic pain is a clinical description (not a diagnosis) which requires a demonstrable lesion that satisfies established neurological diagnostic criteria.
Access information in an overview of pain terminology by the International Association for the Study of Pain.
nociceptive pain
Pain that arises from actual or threatened damage to non-neural tissue and is due to the activation of nociceptors (high threshold sensory receptors of the peripheral somatosensory nervous system that are capable of transducing and encoding noxious stimuli).
Access information in an overview of pain terminology by the International Association for the Study of Pain.
positive predictive value (PPV)
Indicates how likely it is for someone who tests positive to actually have the disease (true positive). It answers the question, “I tested positive. Does this mean I definitely have the disease?”
Equally, the negative predictive value (NPV) indicates how likely it is for someone who tests negative to not have the disease (true negative). It answers the question “I tested negative. Does this mean I definitely don’t have the disease?”
Access information by the Students 4 Best Evidence.
presenteesim
A workplace situation in which an employee is present for duty but is not fully capable of performing workplace tasks due to an illness or other condition. Reasons for presenteeism include chronic physical or mental illness, use or abuse of medications or drugs, external stress or other difficulties in the employee’s personal life. Presenteeism leads to a loss of productivity for the employee and hidden costs to the employer. In addition, when presenteeism leads to a lack of care and diligence, it may create serous health and safety risks to the employee or to others. See absenteeism.
WOMAC
Western Ontario and McMaster Universities Osteoarthritis Index (requires purchase of a license).
Access information on the Shirley Ryan AbilityLab website.
yellow flags
The flags model has been used to describe risk factors for the development of persistent pain and work disability. Yellow flags are psychosocial indicators suggesting an increased risk of progression to long-term distress, disability and potential drug misuse. They include the patient’s attitudes and beliefs, coping strategies and adopting a passive role during recovery.
Access information in the Clinical Framework for the Delivery of Health Services PDF.