The Physical Examination:We appreciate the art…What is the evidence?

Ricardo Jose Gonzalez-Rothi MDDepartment 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 trajectoryEgyptians describe pulse and heartpalpation

“Hippocratic” physicians describe inspection,direct auscultation of organs, palpation, examine bodily secretions

• 200 AD

“Galenic” period: pulse, nerves and muscles, followed by stagnation through Medieval andPost-Renaissance periods

• 1700-1800’s

Hales, Auenbrugger, Laennec, Stokes, Adams, Pasteur, McKenzie, Traube et al…

• 1980’s,90’s

• 3500-1500 BC

• 460 BC

“i-Patients”

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?

A radical proposition…

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 limitationsof 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 BloodPressure and Pulsein Hypovolemia

Jugular Vein Distention inVolume overload states and/or diminished cardiacVentricular function

PEX: Orthostatic BP and Pulse in detecting hypovolemia

from acute blood loss*

Procedure: 1) measure BP, Pulse after 2 min. supine2) 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

CALibratedFingerRubAuditoryScreeningTestD. Torres-Rusotto et al. Neurology 2009 Vol 72 p 1595

442 ears tested

Sound intensity of FingerRub and subjectsAssessed by audiometry

Sensitivity, specificity, LR’s and interobserverreliability assessed

~70 cm

~35cm

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 cliniciansexamining 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 (intermittentfriction rubs, etc)

• Examiner carelessness

• Clinician Bias (loud P2)

Interobserver agreement (К)

PEX Finding К Value

Tachycardia (>100/bpm) 0.85Normal bowel sounds 0.36Peripheral pulse (absent/present) 0.52-0.92

(normal/diminished) 0.01-0.15CALFRAST 0.83Abdominal rigidity 0.14Liver span >9cm (percussion) 0.11Increased tactile fremitus 0.01Diaphragmatic excursion (percussion) -0.04!!!

Interobserver agreement (К)

Technology К Value

Chest X ray (Cardiomegaly) 0.48(Interstitial edema) 0.83

Cardiac Cath (extent CAD stenosis) 0.33

MRI (lumbar root compression) 0.83

Pathology, Liver biopsy (ETOH cirrhosis) 0.49(Cholestasis) 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 ProbabilityClinical 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?

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%

Chunilal et el JAMA 2003 Vol 290 p 2849

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 patientswith a diagnosis who have the particularPEX finding

Specificity is the proportion of patients withoutthe diagnosis who don’t have the particularPEX finding

Sensitivity and Specificity describe thediscriminatory strength of PEX findings.

BIOSTATSPEAK“ A test is valid if it detects most people withthe target disorder (high sensitivity) and excludesmost 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 testare virtually constant,

the positive(PPV) and negative (NPV) predictivevalues when calculated depend crucially on prevalence ( e.g.pre-test probability).

*

* Effect prevalence change on PPV witha test which is 95% Sensitive and Specific

The Likelihood Ratio is a statisticalexpression

which provides the likelihood of a particular PEX findingoccurring in someone with a disorderrelative tothe likelihood of the same finding occurring in someone without the disorder

Towards a more rapid and robust measure of accuracy…

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 + + 15%5.0 + + 30%

10.0 + + 45%

0.5 - - 15%0.2 - - 30%0.1 - - 45%

EXAMPLE: PRE=TEST PROB= 20%, LR=10.0 POST-TEST PROB 20+45= 65%

Bayesian ThinkingThe 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 lossvs 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%

B: Pretest Prob=40%

LR + = 16.8 BC>AC

LR - = 0.2 AC>BC

LR+

LR -

A

B

Cardiac PEX: JugularVenous Distention

Exam Maneuver LR + LR-(vs Gold Standard)

JVD > 3cm

(CVP > 8 cm H2O) 9.0 NS

(ELEVATED LVEDP) 3.9 NS

(LOW EJECTION FRACTION) 7.9 NS

ABDOMINOJUGULAR TEST (aka HJR)

(ELEVATED LVEDP) 8.0 0.3

Chest PEX and airway obstructionPEX 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 ExaminationJAMA 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.htmlSmartphone Apps: upcoming www.medicinetoolkit.com (?)