|
| |
|
Jarrod Shapiro, DPM
Practice Perfect Editor
Assistant Professor,
Dept. of Podiatric Medicine,
Surgery & Biomechanics
College of Podiatric Medicine
Western University of
Health Sciences,
St, Pomona, CA |
How Accurate Is Your Clinical Exam? Part 2
Last issue, I posed our title question, how accurate is your clinical examination? In our modern medical world of evidence-based medicine, it is incumbent upon us to question our methods. As such, I asked how we know various physical examination techniques are truly predictive of the appropriate diagnosis. For example, how accurate is the Mulder’s click in predicting Morton’s neuroma? Questions such as this are answered by looking to the medical literature. Last week , we reviewed the statistical basis for the descriptive terminology when discussing the reliability of clinical tests. Today, we’ll look at some common clinical tests. I think you’ll find it interesting to see just how “accurate” they are.
Reliability
Before we get to the research, there is one final concept to discuss: reliability. As discussed previously, a test is considered reliable if it accurately predicts the presence of a particular disease (best determined by comparing the test to a reference standard). This is the validity of the test. However, it is also important to determine if a test can be repeated with high fidelity by the same person (termed intra-rater reliability) and by other examiners (inter-rater reliability). The statistical methods used to describe these terms are the intraclass correlation coefficient (ICC) and the Kappa coefficient. Although not the same thing, these two statistics can be considered interchangeable. The interpretation is listed in the table below. An ICC or Kappa of 1 indicates perfect agreement, while a value of zero indicates equivalency by chance.
Intraclass correlation coefficient and associated interpretation.
ICC or Kappa |
Interpretation |
.81-1.0 |
True-positive result (a) |
.61-.80 |
Moderate agreement |
.41-.60 |
Fair agreement |
.11-.40 |
Slight agreement |
.0-.1 |
No agreement beyond chance |
On To The Research!
Listed below is a table of physical examination techniques with associated interrater ICC’s demonstrating reliability. This table was taken from an interesting study by Gheluwe, Kirby, et al. (see below for the full citation).
Reliability of selected clinical examination techniques (Gheluwe, Kirby, et al. 2002):
It’s interesting to note just how low the ICCs are for all of these examination techniques. None of these values goes beyond the moderate agreement level, indicating here the relatively low reliability of obtaining the same measurement between examiners. My measurement of first ray motion is very unlikely, for example, to agree with anyone else’s measurements. This is bad news, considering how much we rely on these inaccurate examination techniques when treating our patients.
I’d like to finish our discussion of the physical examination by surveying one additional example, palpating pulses in predicting peripheral arterial disease (PAD). Criqui, et al, in the journal Circulation, reported the data in the table below.
Sensitivity, specificity, and predictive value of pedal pulses in predicting large vessel peripheral arterial disease (all values in %) (Criqui, et al 1985).
Exam |
Sensitivity |
Specificity |
+ Predictive value |
- Predictive value |
Abn posterior tibialis pulse |
71.2 |
91.3 |
48.7 |
96.5 |
Abn dorsalis pedis pulse |
50.0 |
73.1 |
17.7 |
92.7 |
These researchers found that palpating a posterior tibial pulse had a reasonably high sensitivity and high specificity with a strong negative predictive value for large vessel PAD (the single best physical examination technique compared with several other methods including the presence of claudication). However, despite its high specificity in predicting PAD (rather than some other disease causing lower extremity pain) it was more accurate in ruling out PAD than in ruling it in. How does this information help us? It tells us that when we are able to palpate a posterior tibialis pulse in a patient, we can be highly confident that our patient does not have large vessel PAD. However, the absence of a PT pulse does not allow us to rule in PAD, and we should obtain further testing.
A full discussion of testing precision, accuracy, and reliability of our various examination techniques is beyond the scope of this article, but I hope I demonstrated the ability of our research and statistical techniques to call into question those concepts we take for granted. By the way, that Mulder’s click we use to diagnoses Morton’s neuromas? There’s no study that demonstrates the validity of this exam technique. Consider that the next time you schedule your next neurectomy. Best wishes.
Keep writing in with your thoughts and comments. Better yet, post them in our eTalk forum.
Best wishes.
Jarrod Shapiro, DPM
PRESENT Practice Perfect Editor
[email protected]
References:
- Cirque M, et al. The sensitivity, specificity, and predictive value of traditional clinical evaluation of peripheral arterial disease: results from noninvasive testing in a defined population. Circulation, 1985; 71(3): 516-522.
- Gheluwe B, Kirby K, et al. Reliability and Accurace of Biomechanical Measurements of the Lower Extremities. JAPMA, June 2002; 92(6): 317-326.
Get a steady stream of all the NEW PRESENT Podiatry
eLearning by becoming our Facebook Fan.
Effective eLearning and a Colleague Network await you. |
 |
This eZine was made possible through the support of our sponsors: |
|
