The Physical Examination:
We appreciate the art…
What is the evidence?
Ricardo José Gonzalez-Rothi MD
Department of Clinical Sciences
The Art: Reasons for
examining the patient…
Reason # 1:
“ To impress the patient.”
Reason # 2
“To impress, not the patient, but anyone watching you…”
The Ritual…
“Examining the patient…has the ingredients of a ritual:
performed in a special space;
involves one person baring soul…body..
allowing another the privilege of touch…
the person examining wearing a special uniform…
performs a systematic examination…
steps are mysterious to the patient…
using instruments
that are the tokens and talismans of the profession.”
Dr. A Verghese
What I wish to share today:
• Provide a historical trajectory of the
Physical Examination (PEX)
• Discuss how PEX as a “diagnostic test”
can be subjected to rigorous evidence
base regarding reliability and accuracy
• Discuss PEX findings in light of their
diagnostic accuracy in
ascertaining/excluding certain conditions
Physical Examination: a historical trajectory
• 35001500 BC
• 460 BC
• 200 AD
Egyptians describe pulse and heart
palpation
“Hippocratic” physicians describe inspection,
direct auscultation of organs, palpation, examine bodily
secretions
“Galenic” period: pulse, nerves and muscles,
followed by stagnation through Medieval and
Post-Renaissance periods
Hales, Auenbrugger, Laennec, Stokes, Adams,
Pasteur, McKenzie, Traube et al…
• 1700-1800’s
• 1980’s,90’s
“i-Patients”
A radical proposition…
Physical Exam findings should be looked on
as individual “diagnostic tests”.
We subject serum potassium measurements
to scientific exactitude, demanding accuracy
and reliability in measurement and
interpretation.
Should we not do the same with the PEX?
Empiric generalizations about
Physical findings
• A PEX* finding characteristic of a
suspected diagnosis when present, makes
the diagnosis more likely.
• Absence of the characteristic finding
makes the suspected diagnosis less likely.
• Positive/Negative PEX findings shift the
probability of detecting disease
(diagnostic accuracy).
* If objectively validated against “gold standard”
“Time-honored” PEX findings may
be of poor/no diagnostic value…
• Nailbed pallor for anemia
• Barrel Chest for airway obstruction
• Diaphragmatic excursion
“A good clinician must know the limitations
of the physical examination…”
D. Harry, in Magnum Force
What Determines how good the
PEX is?
Is it based on sound anatomic/physiologic principle(s)?
Does it measure what it claims to measure?
Orthostatic Blood
Pressure and Pulse
in Hypovolemia
Jugular Vein Distention in
Volume overload states
and/or diminished cardiac
Ventricular function
PEX: Orthostatic BP and Pulse in detecting
hypovolemia
from acute blood loss*
Procedure: 1) measure BP, Pulse after 2 min. supine
2) measure (1 min? 2 min? after standing)
3) record endpoint(s) (BP, Pulse)
Results: a) A drop in SBP> 20mm Hg has NO proven
value
b) A postural increase in 30 bpm correlates with
“large volume loss” (630-1150 ml blood phlebotomy)
* Baraff and Schriger, Am J. Emerg Med 1992 Vol 10 p 99,
Witting et al Ann Emerg. Med 1994 Vol 23 p 1320
CALibratedFingerRubAuditoryScreeningTest
D. Torres-Rusotto et al. Neurology 2009 Vol 72 p 1595
442 ears tested
Sound intensity of Finger
Rub and subjects
Assessed by audiometry
~70 cm
~35cm
Sensitivity, specificity,
LR’s and interobserver
reliability assessed
Factors influencing Diagnostic
Accuracy of a test
• Reliability
• Pre-test probability
• Sensitivity
• Specificity
What Determines how good the
PEX is?
Reliability: extent of agreement among multiple clinicians
examining the same patients of the absence/presence of
PEX findings in those patients(inter-observer agreement).*
* Not that simple…
Concurrence by chance alone…
Dr. “A” and Dr “B” examine 100 patients with dyspnea.
“Gonzo maneuver” is present in 10, and absent in 70. (present
in 10+ absent in 70=80) or 80% “Simple Agreement”
But: Simple Agreement can be influenced CHANCE ALONE
Especially when Drs A and B both agree on the finding as very
“Uncommon” (near to 0%) or very “Common”(near 100%).
There is a STATISTIC that accounts for CHANCE ALONE in
assessing reliability (К) kappa Statistic
К Statistic and interobserver
agreement (Range 0-1)
К Value
Degree of Agreement
0
CHANCE ALONE
0-0.2
Slight
0.2-0.4
Fair
0.4-0.6
Moderate
0.6-0.8
Substantial
0.8-1.0
Near Perfect
Lack of agreement: PEX
• Physical sign ambiguous and/or vague
(“normal” vs “diminished”)
• Flawed technique
• Biologic variation (intermittent
friction rubs, etc)
• Examiner carelessness
• Clinician Bias (loud P2)
Interobserver agreement (К)
PEX Finding
Tachycardia (>100/bpm)
Normal bowel sounds
Peripheral pulse (absent/present)
(normal/diminished)
CALFRAST
Abdominal rigidity
Liver span >9cm (percussion)
Increased tactile fremitus
Diaphragmatic excursion (percussion)
К Value
0.85
0.36
0.52-0.92
0.01-0.15
0.83
0.14
0.11
0.01
-0.04!!!
Interobserver agreement (К)
Technology
Chest X ray (Cardiomegaly)
(Interstitial edema)
Cardiac Cath (extent CAD stenosis)
К Value
0.48
0.83
0.33
MRI (lumbar root compression)
0.83
Pathology, Liver biopsy (ETOH cirrhosis)
(Cholestasis)
0.49
0.40
Factors influencing Diagnostic
Accuracy of a test
• Reliability
• Pre-test probability
• Sensitivity
• Specificity
Pre-test Probability (PTP):
Diagnostic Accuracy
• Refers to the probability of the disease (prevalence)
before a diagnostic test (PEX) is applied
• Generally PTP is used as first step in clinical
decision-making
Pre-Test Probability
Clinical Situation
Diagnosis
Pre-Test Probability
Cough, fever
Pneumonia
12-30%*
Acute Abdominal pain
Cholecystitis
5%
Dysuria, inc. frequency
Urinary tract Infection
50%
Clinician’s Gestalt?
Chunilal et el JAMA 2003 Vol 290 p 2849
Pre-Test Probabilities for Pulmonary Embolism
Clinician Gestalt
Clinical Prediction Rule
Low
8-19%
3-28%
Moderate
26-47%
16-46%
High
46-91%
38-98%
The Pre-Test Probability is a
start of the diagnostic
processs…but it is not good
enough.
Factors influencing Diagnostic
Accuracy of a test
• Reliability
• Pre-test probability
• Sensitivity
• Specificity
Sensitivity refers to the proportion of patients
with a diagnosis who have the particular
PEX finding
Specificity is the proportion of patients without
the diagnosis who don’t have the particular
PEX finding
Sensitivity and Specificity describe the
discriminatory strength of PEX findings.
BIOSTATSPEAK
“ A test is valid if it detects most people with
the target disorder (high sensitivity) and excludes
most
people without the disorder (high specificity)
and
if a positive test usually indicates that the disorder
is
present (high positive predictive value).”
Greenhalgh, BMJ 1997 Vol 315 p540
“ Lies, damned lies and
statistics…”
not Disraeli
While sensitivity and specificity of a test
are virtually constant,
the positive(PPV) and negative (NPV) predictive
values when calculated depend crucially on
prevalence ( e.g.pre-test probability).
*
* Effect prevalence change on PPV with
a test which is 95% Sensitive and Specific
Towards a more rapid and robust
measure of accuracy…
The Likelihood Ratio is a statistical
expression
which provides the
likelihood of a particular PEX finding
occurring in someone with a disorder
relative to
the likelihood of the same finding
occurring in someone without the disorder
Likelihood Ratios (LR) describe
discriminatory power of PEX findings
• A SINGLE number, unaffected by prevalence
• Simple to use, calculated from Sensitivity and
Specificity values
• Accurate
• Can be applied to PEX findings of continuous scale
(BP), or ordinate scale (e.g. 1+, 2+)
• Can be used to combine PEX findings*
Likelihood Ratios (LR)
• Expressed as LR “+” (PEX finding present) or
LR “-” (PEX finding absent)
• LR’s > 1 increase probability of presence of
disease*
• The higher the LR the greater the compelling
power that the PEX confirms a disease
• LR=(0-1) decrease the probability of presence
of disease*
* Assuming the 95% Confidence intervals appropriate
LR: rule of thumb…
LR
+/- change in post-test probability
2.0 +
5.0 +
10.0 +
+ 15%
+ 30%
+ 45%
0.5 0.2 0.1 -
- 15%
- 30%
- 45%
EXAMPLE: PRE=TEST PROB= 20%, LR=10.0
POST-TEST PROB 20+45= 65%
Bayesian Thinking
The probability of diagnosing a disease
following the interpretation of a diagnostic
test (post-test probability) is based on 2
factors:
1) The Pre-test probability (prevalence of
disease)
2) How accurate (and reliable) the diagnostic
test itself is*
• VS “Gold Standard”
Rinne Test: Hearing loss
vs Audiometry=gold standard
BC> AC= CONDUCTIVE
LOSS
Likelihood Ratio (+) = 16.8
*
Likelihood Ratio (-) = 0.2
*Burkey et. al. Am J. Otol 1993 Vol 19 p 59,
Chole et al. Arch Otolaryngol Head Neck Surg 1988 Vol 114 p 399
FAGAN NOMOGRAM
Condition: Unilateral
hearing loss
Rinne Test:
A: Pretest Prob=20%
LR+
B: Pretest Prob=40%
A
LR + = 16.8 BC>AC
LR - = 0.2 AC>BC
B
LR -
Cardiac PEX: Jugular
Venous Distention
Exam Maneuver
(vs Gold Standard)
LR +
LR-
(CVP > 8 cm H2O)
9.0
NS
(ELEVATED LVEDP)
3.9
NS
(LOW EJECTION FRACTION)
7.9
NS
JVD > 3cm
ABDOMINOJUGULAR TEST (aka HJR)
(ELEVATED LVEDP)
8.0
0.3
Chest PEX and airway obstruction
PEX FINDING
LIKELIHOOD RATIO
Early Inspiratory coarse crackles
14.6
Absence of Cardiac Dullness LSB
11.2
Breath sound score < 9
10.2
Snider Test (blow out match)
9.6
Subxyphoid Cardiac Impulse
7.4
Hyperresonance RU Anterior chest
5.1
Reduced Diaphragmatic Excursion
NS
What I shared today:
• Historical trajectory of the Physical
Examination (PEX)
• How PEX as a “diagnostic test” can be
subjected to rigorous evidence base
regarding reliability and accuracy
• Discussed PEX findings in light of their
diagnostic accuracy in ascertaining/excluding
certain conditions
Additional Resources
“on papyrus”:
• Simel DL and Rennie D. The Rational Clinical Examination
JAMA evidence, McGraw Hill Medical Press, 2009.
(mcgraw-hillmedical.com)
• McGee S. Evidence Based Physical Diagnosis, Saunders
Elsevier, second edition 2007.
“on line” :
• Essential Evidence Plus (available to FSUCOM Library, PDA’s)
• Statistical Calculators:
www.mclibrary.duke.edu/subject/ebm/ratios.html
Smartphone Apps: upcoming www.medicinetoolkit.com (?)