Clinical Trials - Sensitivity, Specificity, Validity & More.
August 28, 2019
For issues and complaints related to the human body, musculoskeletal system, and musculoskeletal system, we at BodyLab, Osteopathy, Physiotherapy, Rehabilitation, and Training Zurich are the experts.
Whether with or without a medical referral, patients come to us hoping for our help or support.
Our first task is to determine where and in which structure the problem lies. Even medical diagnoses often only describe approximately (or not at all) where the problem is. For example, a lumbar spine syndrome or lumbago only indicates that there are problems, complaints, or pain in the lower back. An epicondylitis (tennis elbow), for instance, says nothing about its cause. The issue could be muscular (then the question arises in which muscle and where exactly) or it could be in the tendon or the bone-tendon junction. Countless such examples can be given...
An examination always begins with a detailed anamnesis, where the patient's subjective problems and complaints are recorded. Where is the problem and the pain? When does it appear, what triggers it, and what helps or feels good? Is it unilateral or bilateral, are there any radiations, paresthesias, and the timeline and progression since the onset of the problem? Was there a triggering event (trauma, overuse), what are the normal activities (ADL, occupation, hobbies), and what is still possible and what is not. Also of interest are previous illnesses, injuries, surgeries, dietary habits, etc.
This includes the social and family history (family background, the load-bearing capacity of the system), whether medications are necessary or being taken, as well as identifying yellow and red flags are some important points that need to be explored, as we will see later.
During this process, the osteopath or physiotherapist already forms various hypotheses based on their knowledge and clinical experience.
Through clinical reasoning, functional and movement examination, and various diagnostic tests, the hypotheses and complaints obtained during the anamnesis are objectified.
As the saying goes "measurement is expressing nonsense if done wrong," it is crucial to use the right and appropriate tests, otherwise they do not help at all. We would like to explain this a bit further here.
To understand this, here is a symbolic comparison: If you went fishing in a lake (like Zurichsee) with a large-mesh fishing net, you would only catch very large fish or perhaps none at all. And you might think that there are only large fish in that lake, which of course, is not true. But such a net would not be sensitive enough and not valid for this lake to catch small fish.
Therefore, after the anamnesis, you must consider through good clinical reasoning:
What do I want to measure?
Am I measuring/testing correctly?
Do I have the ideal measuring tool?
Sensitivity / Specificity / Validity
-> NB: Be sure to work with hypotheses derived from the anamnesis!
Measuring instruments and orthopedic or manual clinical tests should be viewed as such; they can be divided according to various criteria:
Sensitivity
Specificity
Validity
Reliability
Therefore, and to select the right clinical test, a good and comprehensive anamnesis with a subsequent working hypothesis (therapeutic diagnosis) is immensely important!
Sensitivity
Sensitivity (also known as hit rate or true positive rate) of a diagnostic test provides information about how likely a positive test result is in a person who has the problem. More precisely, it shows what proportion of diseased patients actually have the disease detected by the test, resulting in a positive test result.
The higher the sensitivity of a test, the more reliably it detects the disease.
Specificity
The specificity of a test indicates how likely a negative test result is in healthy individuals (without disease or injury).
This represents the probability that truly healthy individuals who do not have the specific disease are recognized as healthy by the test.
Validity
Validity provides information about whether a test measures exactly what you want to measure. It is valid if it actually measures what it is intended to measure.
Reliability
Reliability represents the accuracy and consistency of a test. This means whether a test would achieve the same result upon repetition under the same conditions (reproducibility).
A test is reliable if it achieves the greatest possible similarity upon repeated application and thus the result is not dependent on chance.
Objectivity
Objectivity of a test refers to the independence of the results from external conditions and distorting third factors.
Responsiveness
This is the sensitivity to response. It determines the ability of a measurement to show (measure) significant clinical changes over time. Possibly important for monitoring the progress of therapy!
NB: Higher sensitivity (towards 100%) is only achieved by reducing threshold values; however, this comes at the expense of specificity!!
As can be easily seen, individual, unrelated clinical tests make little sense and yield no results or say little about a problem. A big issue for inexperienced therapists! And too many tests provoke and irritate injured structures as well, possibly preventing a clear result from being determined.
Based on the hypothesis (or hypotheses) developed from the anamnesis and clinical reasoning, the right diagnostic tests should be selected – and they should also be correctly conducted. This also means that a therapist must know what a clinical test can and cannot do, and its purpose! Is it positive if pain occurs or is triggered? Or is an impermissible range/motion a positive sign? Or is a diminutive or untriggered reflex a positive sign?
Clinical tests should also be conducted in the correct order to be optimally interpreted.
Clinical Tests: Optimal Order and Procedure
Screening Test (high sensitivity)
-> to rule out pathology when they are negative
Validation Test (high specificity)
-> Negative result should mean that the cause is indeed not present
Exclusion Test (high specificity)
Provoking or Reducing Test
Mechanical Test
Initially, a test should be conducted that has high sensitivity and specificity for the relevant structure, to determine whether there is a problem there. Then a test with high validity should follow to test exactly this structure! Exclusionary or provoking tests complement the examination. The result can be verified with mechanical tests.
Scientific Studies on Medical Clinical Tests
From our perspective, therapists should always engage in critical reflection on their thinking and actions.
There are always studies and publications in the literature examining the accuracy and validity of clinical tests. The book Orthopedic Physical Examination Tests: An evidence-based Approach by Chad E. Cook and Eric J. Hegedus is a standard reference on manual examination tests.
One should check and control their results through objectification – and document them. With some practice and experience, this doesn’t take too much time!
Here is (an incomplete) selection of practical tests for various issues from our perspective – also for the therapeutic workday:
Goniometer: For the range of motion
Manual Muscle Testing: Manual muscle strength measurement
Visual Analog Scale (VAS): For example, for pain
Coping Strategies Questionnaire: Assess pain management
Short-Form McGill Pain Questionnaire: Evaluate pain
Disabilities of the Arm, Shoulder, and Hand (DASH or Quick DASH): Assess arm complaints and capabilities
Shoulder Pain and Disability Index: Assess shoulder complaints
Berg Balance Scale: An insightful test for balance
POMA Tinetti Test: Identify fall risk
Dynamic Gait Index: Assess walking balance
Timed Walking Tests: Objectively measure locomotion
Timed Up and Go Test: Stand up, walk with a turn
Sharp Purser Test: Test upper cervical spine stability
Borg Scale: How strenuous is this for you? Measure subjective exertion
6-Minute Walk Test: Improved performance?
3-Minute Step Test: The fitness check
Conconi Test: Determine aerobic performance capacity
Goal Attainment Scale (GAS): Objectively measure subjective goals
Chedoke McMaster Stroke Assessment: Post-stroke
Trunk Impairment Scale: Assess trunk stability after stroke
Further practical clinical tests can be found on the website of the IGPTR Interessengemeinschaft Physiotherapie Rehabilitation.
Through objective measurements, therapy results and therapy progress can be clearly and better reviewed and documented. And changes that might not be noticed by either patients or therapists can be detected with adequate tests.
To recap: It is important to carefully consider what and which clinical tests or measuring tools one wants to use for which problem. Since these tests are not inherently valid for every issue!
Test results are not set in stone and are continually reviewed, even during treatment. Therapeutic interventions are thus repeatedly checked and, if necessary, adapted through retests and by observing the treatment outcome!
As you can see, the human body and manual medicine are not simple. But that's what makes them exciting. And it's definitely worth getting a dedicated, good, and competent therapist.
As I said, who measures measures nonsense if done incorrectly.
If you need us, we are here for you!
Your BodyLab Team – Your Specialists after Physical Injuries
Osteopathy and Physiotherapy | Rehabilitation and Training
Zurich Altstetten
Literature References
Orthopedic Physical Examination Tests: An evidence-based Approach
Chad E. Cook, Eric J. Hegedus
2008 by Pearson Education Inc., Upper Saddle River, New Jersey 07458
IGPTR Interessengemeinschaft Physiotherapie Rehabilitation
