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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_2716_Библиотеки_им_академика_М_И_Перельмана
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4—USING THE ONLINE EBM CALCULATOR
A
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29
Problems:
Pretest probability:
Problems:
Pretest probability:
Problems:
Blank Calculator
Goiter
Hemorrhagic stroke
Hepatomegaly
Hepatopulmonary syndrome
Hip arthritis
Hyperthyroidism
Hepatopulmonary syndrome
10%
Hepatopulmonary syndrome
ndromeorner syH
Range
10%
Median
30%0% 20% 40% 50% 60% 70% 80% 90% 100%
View LR Value
100%90%80%70%60%50%0% 20% 30% 40%
40%30%20%
R Valueiew LV
View LR Value
Pretest probability:
−
ratio:kelihoodLi
LRs
Fig. 4.2 Diagnosing hepatopulmonary syndrome with the EBM Calculator. The clinician is evaluat-
ing a patient with cirrhosis and clubbing and wonders about the likelihood of hepatopulmonary syndrome.
Selecting hepatopulmonary syndrome (top left) reveals the pre-test probability in clinical studies ranges from
14% to 37%, with a median probability of 26% (middle left). Believing hepatopulmonary syndrome to be more
prevalent in his own practice than 26%, the clinician drags the pre-test probability arrow to 30% (middle
left), clicks view LR value (bottom left) to reveal the LR for clubbing (LR = 4.3). Dragging the LR arrow to 4.3
demonstrates the post-test probability of hepatopulmonary to be approximately 65% (right).
PHE AT ARULMONOP Y MENDROSY
Probability
Decrease Increase
−
−
15%
30%
45%
0.1 0.2 0.5 12510
0.50.02 0.05 0.1 0.20.01 1251 20 0
Cyanosis
Clubbing
+45%+30%+15%
100%90%80%70%60%50%40%30%0% 20%
LRs
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2—UNDERSTANDING THE EVIDENCE
Problems:
Pretest probability:
Likelihood ratio:
Posttest probability:
Hepatopulmonary syndrome
0.50.20.10.050.020.01 1251020
View LR Value
100%90%80%70%60%50%40%30%20%10%0%
100%90%80%70%60%50%40%30%20%10%0%
B
Continued
Fig. 4.2
is 4.3. After dragging the LR arrow to 4.3, the calculator indicates that the post-test probability
of hepatopulmonary syndrome (in this clinician’s patient with cirrhosis and clubbing) is 65%
(Fig. 4.2).
Following the rules discussed in Chapter 2, the clinician may combine findings using this
calculator by simply transferring the post-test probability from the first finding to the pre-test
probability rule of the second finding. (See the section on Combining Findings in Chapter 2.)
CHAPTER
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Reliability of Physical Findings
KEY TEACHING POINTS
• Reliability refers to how often two clinicians examining the same patient agree about the
presence or absence of a particular physical finding. Commonly used measurements of
reliability are simple agreement or the kappa (κ-) statistic.
• About 60% of physical findings have κ-statistics of 0.4 or more, indicating that observed
agreement is moderately good or better.
• Despite the common belief that technologic tests are more precise than bedside
observation, the κ-statistics observed for most diagnostic standards (e.g., chest
radiography, computed tomography, angiography, magnetic resonance imaging,
endoscopy, and pathology) are similar to those observed for physical signs.
• Some causes of interobserver disagreement can be eliminated, but because clinical
medicine is inherently a human enterprise (even when interpreting technologic tests),
subjectivity and a certain level of clinical disagreement will always be present.
5
Reliability refers to how often multiple clinicians, examining the same patients, agree that a particular physical sign is present or absent. As characteristics of a physical sign, reliability and accuracy are
distinct qualities, although significant interobserver disagreement tends to undermine the finding’s
accuracy and prevents clinicians from applying it confidently to their own practice. Disagreement
about physical signs also contributes to the growing sense among clinicians, not necessarily justified,
that physical examination is less scientific than more technologic tests, such as clinical imaging and
laboratory testing, and that physical examination lacks their diagnostic authority.
e most straightforward way to express reliability, or interobserver agreement, is simple
agreement, which is the proportion of total observations in which clinicians agree about the finding. For example, if two clinicians examining 100 patients with dyspnea agree that a third heart
sound is present in 5 patients and is absent in 75 patients, simple agreement would be 80% [i.e.,
(5 + 75)/100 = 0.80]; in the remaining 20 patients, only one of the two clinicians heard a third
heart sound. Simple agreement has advantages, including being easy to calculate and understand,
but a significant disadvantage is that agreement may be quite high by chance alone. For example, if
one of the clinicians in our hypothetical study heard a third heart sound in 10 of the 100 dyspneic
patients and the other heard it in 20 of the patients (even though they agreed about the presence
of the heart sound in only 5 patients), simple agreement by chance alone would be 74%.* With
chance agreement this high, the observed 80% agreement no longer seems so impressive.
To address this problem, most clinical studies now express interobserver agreement using the
kappa (κ) statistic, which usually has values between 0 and 1 (the Appendix at the end of this
*Agreement by chance approaches 100% as the percentage of positive observations for both clinicians
approaches 0% or 100% (i.e., both clinicians agree that a finding is very uncommon or very common). e
Appendix at the end of this chapter shows how to calculate chance agreement.
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2—UNDERSTANDING THE EVIDENCE
chapter shows how to calculate the κ-statistic). A κ-value of 0 indicates that observed agreement
is the same as that expected by chance, and a κ-value of 1 indicates perfect agreement. According
to convention, a κ-value of 0 to 0.2 indicates slight agreement; 0.2 to 0.4 fair agreement; 0.4 to
0.6 moderate agreement; 0.6 to 0.8 substantial agreement; and 0.8 to 1.0 almost perfect agreement.†
TABLE 5.1 ■ Interobserver Agreement and Physical Signs
Finding (ref) κ-statistic*
General Appearance
Mental status examination
Mini-Mental Status Examination
Clock-drawing test (Wolf-Klein Method)
Confusion Assessment Method for delirium
Altered mental status
Stance and gait
Abnormal gait
7
8,9
Skin
Patient appears anemic
Nailbed pallor
Conjunctival pallor (rim method)
Palmar crease pallor
Ashen or pale skin
Cyanosis
Jaundice
Loss of hair
Vascular spiders
Palmar erythema
12
14
7
10,15
16
17
16–18
16–18
Hydration status
Patient appears dehydrated
Axillary dryness
19
Increased moisture on skin
Capillary refill > 3 seconds
Capillary refill > 5 seconds
Nutritional assessment
Abnormal nutritional state
Other
Consciousness impaired
Patient appears older than age
Patient appears in pain
Generally unwell in appearance
Vital Signs
Tachycardia (heart rate >100/min)
Bradycardia (heart rate <60/min)
Systolic hypertension (SBP>160 mm Hg)
Hypotension (SBP <90 mm Hg)
Osler sign
23–25
Rumpel-Leede (“tourniquet”) test
Elevated body temperature, palpating the skin
Tachypnea
7,15,21
10
10,11
10
1
2
3–6
0.28–0.80
0.73
0.70–0.91
0.71
0.11–0.71
0.23–0.48
13,14
0.19–0.34
0.54–0.77
0.44
0.34
0.36–0.70
0.65
0.51
0.64–0.92
0.37–1.00
10
10
7
20
10
10
10
21
21
21
21,22
26,27
10
0.44–0.53
0.50
0.31–0.53
0.29
0.74–0.91
0.27–0.36
0.65–0.88
0.38–0.42
0.43–0.75
0.52–0.64
0.85
0.87
0.75
0.27–0.90
0.26–0.72
0.76–0.88
0.09–0.23
0.25–0.60
†
No measure of reliability is perfect, especially for findings whose prevalence clinicians agree approaches
0% or 100%. For these findings, simple agreement tends to overestimate reliability, and the κ-statistic
tends to underestimate the reliability.
Continued
5—RELIABILITY OF PHYSICAL FINDINGS
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TABLE 5.1 ■ Interobserver Agreement and Physical Signs
—Cont’d
Finding (ref) κ-statistic*
Head and Neck
Pupils
Swinging flashlight test (relative afferent pupil defect)
Diabetic retinopathy
Microaneurysms
Intraretinal hemorrhages
Hard exudates
Cotton wool spots
Intraretinal microvascular abnormalities (“IRMA”)
Neovascularization near disc
Macular edema
Overall grade
Hearing
Whispered voice test
Finger rub test
29,30
29,30
29,30
29,30
29,30
29,30
29,30
31,32
33
Thyroid
Thyroid gland diffuse, multinodular or solitary nodule
35,36
Goiter
Meninges
Nuchal rigidity, present or absent
37–39
29,30
28
0.63
0.58–0.66
0.89
0.66–0.74
0.56–0.67
0.46
0.21–0.48
0.21–0.67
0.65
0.16–1.0
0.83
34
0.25–0.70
0.38–0.77
0.24–0.76
Lungs
Inspection
Clubbing (general impression)
Clubbing (interphalangeal depth ratio)
Clubbing (Schamroth sign)
Breathing difficulties
10
Gasping respirations
Reduced chest movement
Kussmaul respirations
Pursed lip breathing
43
Asymmetric chest expansion
Scalene or sternocleidomastoid muscle contraction
40
Kyphosis
Barrel chest
Thoracic ratio ≥0.9
Displaced trachea
43
43
15
Palpation
Tracheal descent during inspiration
Laryngeal height ≤5.5 cm
Impalpable apex beat
Decreased tactile fremitus
Increased tactile fremitus
Subxiphoid point of maximal cardiac impulse
Paradoxical costal margin movement
Percussion
Hyperresonant percussion note
Dull percussion note
Diaphragm excursion more or less than 2 cm by percussion
Diminished cardiac dullness
Auscultatory percussion abnormal
7
44
15,40
15
15,42,45,49
41
15,42,43
43
15,45
15,40
41
0.33–0.45
0.98
0.64
0.54–0.69
0.63
0.14–0.38
0.70
45
7,43,46
0.45
0.85
0.52–0.57
0.37
0.62
0.32
0.01
46
0.62
0.59
0.33–0.44
0.24–0.86
47
46,48
15,42,47
47
47
45,50
0.01
0.30
0.56–0.82
0.26–0.50
0.16–0.84
–0.04
0.49
0.18–0.76
Continued
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2—UNDERSTANDING THE EVIDENCE
TABLE 5.1 ■ Interobserver Agreement and Physical Signs
—Cont’d
Finding (ref) κ-statistic*
Auscultation
Reduced breath sound intensity
Bronchial breathing
15,42
Whispering pectoriloquy
Reduced vocal resonance
15,49,51,53–56
Crackles
15,47,49,51,52
Wheezes
42,52
Rhonchi
Pleural rub
Special tests
Snider test <10 cm
Forced expiratory time
Hoover sign
15,45
47
43,47,57,58
52
Wells simplified rule for pulmonary embolism
15
45
15,42,43,45,47,49,51,52
0.16–0.89
0.19–0.32
0.11
0.78
0.21–0.65
0.43–0.93
0.38–0.55
−0.02–0.51
0.39
0.27–0.70
59
0.74
0.54–0.62
Heart
Neck veins
Neck veins, elevated or normal
Abdominojugular test
60
53–55,60,61
0.08–0.71
0.92
Palpation
Palpable apical impulse present
Palpable apical impulse measureable
Palpable apical impulse displaced lateral to midclavicular line
Apical beat normal, sustained, double, or absent
Palpable right ventricular heave
Percussion
Cardiac dullness >10.5 cm from midsternal line
Auscultation
S2 diminished or absent, vs. normal
Third heart sound
Fourth heart sound
53–55,60,70–72
71,73
Systolic murmur, present or absent
Systolic murmur radiates to right carotid
Systolic murmur, long systolic or early systolic
Murmur intensity (Levine grade)
Systolic murmur grade >2/6
Carotid pulsation
Delayed carotid upstroke
Reduced carotid volume
62–64
65
53,62,63,66
66
61
67,68
69
0.68–0.82
0.56
0.43–0.86
0.88
0.18–0.23
0.57
0.54
–0.17–0.84
69
69
74
75
76
69
69
0.15–0.71
0.19
0.33
0.78
0.43–0.60
0.59
0.26
0.24
Abdomen
Inspection
Abdominal distention
Abdominal wall collateral veins, present vs. absent
Palpation and percussion
16,18,55
Ascites
Abdominal tenderness
Surgical abdomen
Abdominal wall tenderness test
Rebound tenderness
77,78
Guarding
77
Rigidity
Abdominal mass palpated
77,78
16
77–79
78
80,81
77
0.35–0.42
0.47
0.47–0.75
0.31–0.68
0.27
0.52–0.81
0.25
0.36–0.49
78
0.14
0.82
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TABLE 5.1 ■ Interobserver Agreement and Physical Signs
—Cont’d
Finding (ref) κ-statistic*
Palpable spleen
Palpable liver edge
Liver consistency, normal or abnormal
Liver firm to palpation
Liver, nodular or not
Liver, tender or not
Liver, span >9 cm by percussion
Spleen palpable or not
Spleen percussion sign (Traube), positive or not
Spleen percussion sign (Castell), positive or not
Abdominal aortic aneurysm, present vs. absent
Auscultation
Normal bowel sounds
16,18,82
83
16
84
16
18
53
85
86
82
87
78
0.33–0.75
0.44–0.53
0.4
0.72
0.29
0.49
0.11
0.56–0.70
0.19–0.41
0.45
0.53
0.36
Extremities
Peripheral vascular disease
Peripheral pulse, present vs. absent
Peripheral pulse, normal or diminished
Cool extremities
55
Severity of skin mottling over leg
Diabetic foot
Monofilament sensation, normal or abnormal
Probe-to-bone test
Edema and deep venous thrombosis
Dependent edema
97–99
53–55
Wells pretest probability for deep vein thrombosis
Musculoskeletal system-shoulder
Shoulder tenderness
Painful arc
102–105
Neer impingement sign
102
106
Hawkins impingement sign
External rotation of shoulder <45 degrees
Supraspinatus test (empty can)
Infraspinatus test (resisted external rotation)
Impingement sign (Hawkins-Kennedy)
Drop arm test
Musculoskeletal system-hip
Patrick test
102,105
108
Passive internal rotation ≤25 degrees
Musculoskeletal system-knee
Ottawa knee rules
Knee effusion visible
Knee flexion <90 degrees
Patellar tenderness
Head of fibula tenderness
Inability to bear weight immediately and emergency room after knee
109,111
injury
Bony swelling of knee
Joint line tenderness
Patellofemoral crepitus
Mediolateral instability of knee
McMurray sign
Lachman test
109,110
109,111–113
109
109,111
109
113,114
112,114–116
114
112,116,117
118
106
92,93
102,105,107
114
88–91
88
102,103,105,107
108
102
94–96
102,103
100,101
0.52–0.92
0.01–0.15
0.46
0.87
0.48–0.83
0.59–0.84
0.39–0.73
0.74–0.75
0.32
0.45–0.64
0.64
0.54
0.68
0.44–0.94
0.49–0.67
0.29–1.0
0.28–0.35
0.47
0.51
0.51–0.77
0.28–0.78
0.74
0.69–0.76
0.64
0.75–0.81
0.55–0.66
0.11–0.43
0.24
0.23
0.16–0.35
0.72
Continued
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2—UNDERSTANDING THE EVIDENCE
TABLE 5.1 ■ Interobserver Agreement and Physical Signs
—Cont’d
Finding (ref) κ-statistic*
Musculoskeletal system-ankle
Inability to walk 4 steps immediately and in emergency room after ankle
119,120
injury
Medial malleolar tenderness
Lateral malleolar tenderness
Navicular tenderness
Base of 5th metatarsal tenderness
Ottawa ankle rule
121,122
Ottawa midfoot rule
120
120
120
120
121
0.71–0.97
0.82
0.80
0.91
0.94
0.41–0.45
0.77
Neurologic Examination
Visual fields
Visual fields by confrontation
Cranial nerves
Pharyngeal sensation, present or absent
Facial palsy, present or absent
Dysarthria, present or absent
Water swallow test (50 mL)
Oxygen desaturation test (for aspiration risk)
Abnormal tongue strength
Motor examination
Muscle strength, MRC scale
Foot tapping test
Muscle atrophy
134,135
136,137
Spasticity, 6 point scale
Rigidity, 4 point scale
16
Asterixis
137
Tremor
Pronator drift
140
Forearm rolling test
Sensory examination
Light touch sensation, normal, diminished, or increased
Pain sensation, normal, diminished, or increased
Vibratory sensation, normal or diminished
Romberg test
137
Reflex examination
Reflex amplitude, NINDS scale
Ankle jerk, present or absent
Asymmetric knee jerk
Babinski response
Finger flexion reflex
Palmomental reflex
125,126,134,135,137,144,145
146
147
Primitive reflexes, amplitude and persistence
Coordination
Finger-nose test
Heel-shin test
Peripheral nerve
Spurling test
Katz hand diagram
Flick sign
Hypalgesia index finger
Tinel sign
Phalen sign
125,126,137,140
137
149
150
151
151
151
123
124
125,126
127,128
129
129
127
130–133
0.63–0.81
1.0
0.57
0.41–0.77
0.60
0.60
0.55–0.63
0.69–0.93
0.73–0.83
138
139
0.32–0.82
0.21–0.61
0.64
0.42
0.74
140
136,137
131,136,137
136,137
0.39
0.73
0.22–0.63
0.41–0.57
0.28–0.54
0.64
141
131,142,143
131
0.51–0.61
0.34–0.94
0.42
0.17–0.60
0.65
148
0.53
0.46–1.0
0.14–0.65
0.58
0.60
0.86
151
0.90
0.50
0.47
0.79
5—RELIABILITY OF PHYSICAL FINDINGS
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TABLE 5.1 ■ Interobserver Agreement and Physical Signs
Finding (ref) κ-statistic*
Straight leg raising test
Crossed leg raising test
Other
Head impulse test
Knee lift test (for nonorganic weakness)
*Interpretation of the κ-statistic: 0 to 0.2 slight agreement, 0.2 to 0.4 fair agreement, 0.4 to 0.6 moderate
agreement, 0.6 to 0.8 substantial agreement, 0.8 to 1.0 almost perfect agreement.
MRC, Medical Research Council; NINDS, National Institute of Neurological Disorders and Stroke.
131,152–156
131
157
158
—Cont’d
0.21–0.80
0.49
0.86
0.91
Rarely, physical signs have κ-values less than 0 (theoretically as low as –1), indicating the observed
agreement was worse than chance agreement.
Table 5.1 presents the κ-statistic for most of the physical signs discussed in this book, dem-
onstrating that, with rare exceptions, observed agreement is better than chance agreement (i.e.,
κ-statistic exceeds 0). About 60% of findings have a κ-statistic of 0.4 or more, indicating that
observed agreement is moderate or better.
Clinical disagreement occurs for many reasons—some causes clinicians can control, but others
are inextricably linked to the very nature of clinical medicine and human observation in general.
e most prominent reasons include the following: (1) e physical sign’s definition can be vague or
ambiguous. For example, experts recommend about a dozen different ways to perform auscultatory
percussion of the liver, thus making the sign so nebulous that significant interobserver disagreement is
guaranteed. Ambiguity also results if signs are defined with terms that are not easily measurable. For
example, clinicians assessing whether a peripheral pulse is present or absent demonstrate moderateto-almost perfect agreement (κ = 0.52–0.92, Table 5.1), but when the same clinicians are asked to
record whether the palpable pulse is normal or diminished, they have great difficulty agreeing about
the sign (κ = 0.01–0.15) simply because they have no idea what the next clinician means by “diminished.” (2) e clinician’s technique is flawed. For example, common mistakes are using the diaphragm
instead of the bell of the stethoscope to detect the third heart sound, or stating a muscle stretch reflex
is absent without first trying to elicit it using a reinforcing maneuver (e.g., Jendrassik maneuver). (3)
Biologic variation of the physical sign. e pericardial friction rub, pulsus alternans, cannon A waves,
Cheyne-Stokes respirations, and many other signs are notoriously evanescent, tending to come and
go over time. (4) e clinician could be careless or inattentive. e bustle of an active practice may
lead clinicians to listen to the lungs while conducting the patient interview, or to search for a subtle
murmur in a noisy emergency room. Reliable observations require undistracted attention and an alert
mind. (5) e clinician’s biases can influence the observation. When findings are equivocal, expectations influence perceptions. For example, in a patient who just started blood pressure medications,
borderline hypertension may become normal blood pressure; in a patient with increasing bilateral
edema, borderline distended neck veins may become clearly elevated venous pressure; or in a patient
with new weakness, the equivocal Babinski sign may become clearly positive. Sometimes, biases actually create the finding: if the clinician holds a flashlight too long over an eye with suspected optic
nerve disease, he or she may temporarily bleach the retina of that eye and produce the Marcus Gunn
pupil, thus confirming the original suspicion.
e lack of perfect reliability with physical diagnosis is sometimes regarded as a significant
weakness, leading to the charge that physical diagnosis is less reliable and scientific than clinical
imaging and laboratory testing. Nonetheless, Table 5.2 shows that, for most of our diagnos-
tic standards—chest radiography, computed tomography, screening mammography, angiography, magnetic resonance imaging, ultrasonography, endoscopy, and pathology—interobserver
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2—UNDERSTANDING THE EVIDENCE
TABLE 5.2 ■ Interobserver Agreement – Diagnostic Standards
Finding (ref) κ-statistic*
Chest radiography
Cardiomegaly
Pulmonary infiltrate
Pneumonia
Interstitial edema
Pulmonary vascular redistribution
Grading pulmonary fibrosis, 4 point scale
Contrast venography
Deep vein thrombosis in leg
Screening mammography
Suspicious lesion, present vs. absent
Digital subtraction angiography
Renal artery stenosis
Coronary arteriography
Classification of coronary artery lesions
Arthroscopy
Inflamed or torn supraspinatus tendon
Computed tomography of head
Normal or abnormal, patient with stroke
Lesion on right or left side, patient with stroke
Mass effect, present or absent
Computed tomography of the chest
Lung cancer staging
Submassive pulmonary embolism present (angiography)
Coronary lesion on CT coronary angiography
Magnetic resonance imaging of head
Compatible with multiple sclerosis
Pituitary microadenoma present
Magnetic resonance imaging of lumbar spine
Intervertebral disc extrusion, protrusion, bulge, or normal
Lumbar nerve root compression
Ultrasonography
Calf deep vein thrombosis, present or absent
Thyroid nodule, present or absent
Thyroid nodule, cystic or solid
Goiter is present
Electrocardiography
Diagnosis of narrow-complex tachycardia
Echocardiography
Severity of valvular regurgitation
Endoscopy
Grade of reflux esophagitis
Pathologic examination of liver biopsy
Cholestasis
Alcoholic liver disease
Cirrhosis
60
159,160
161
60
60
162
163
164
165
166
167
168
168
168
169
170
171
172
173
174,175
175,176
177
178,179
180
36
181
182,183
184
185
185
185
0.48
0.38–0.58
0.45
0.83
0.50
0.45
0.53
0.47
0.65
0.33
0.47
0.60
0.65
0.52
0.40–0.60
0.47
0.57
0.57–0.87
0.30
0.59
0.63–0.83
0.69
0.57–0.66
0.64
0.63
0.70
0.32–0.55
0.55
0.40
0.49
0.59
*Interpretation of the κ-statistic: 0 to 0.2 slight agreement, 0.2 to 0.4 fair agreement, 0.4 to 0.6 moderate
agreement, 0.6 to 0.8 substantial agreement, 0.8 to 1.0 almost perfect agreement.
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