Clinical history and physical examination

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The above case is a common scenario that clinicians face in the outpatient setting. How much information can the history and physical examination provide in making the diagnosis of CAP? A 1997 review14 identified four prospective studies15-18 that applied an independent, blind comparison with a "gold" standard to assess the accuracy of clinical history in diagnosing CAP (Table 6.1). The same four studies also assessed the accuracy of physical examination in diagnosing CAP14 (Table 6.2). The overall conclusion was that no individual element of history or physical examination possesses a likelihood ratio high or low enough to rule CAP in or out. This finding was also supported by a 2003 review of testing strategies in CAP in which the authors reported the ranges of calculated likelihood ratios for studies reporting statistically significant results. 19

The combination of various elements from the history and physical examination has also been evaluated in terms of its ability to accurately predict pneumonia. Diehr et al.15 assigned points based on the presence of each of the following findings: rhinorrhoea (- 2 points); sore throat (- 1 point); night sweats (+ 1 point); myalgias (+ 1 point);

Table 6.1 Diagnosing community-acquired pheumonia from patient history

Sensitivity

Specificity

Positive LR

Negative LR

Reference

Symptoms

Fever (temperature

Cough

Night sweats

Chills

Dyspnea

Sputum production Myalgias Rhinorrhea Sore throat

G63 G83 G33 G^51 G32 G63 G63 G78 G76 G67 G57

G63 G54 G81 G7G G8G G52 G55 G4G G42 G14 G27

18 17 17 16

14 13 13 G78 G78

G-71

G59 G31 G83 G7G G85 G72 G67 G55 G58 24 16

Diehr, 198415

Heckerling, 199018 Singal, 198917 Diehr, 198415 Heckerling, 199018 Diehr, 198415 Gennis, 198816 Gennis, 198816 Diehr, 198415 Diehr, 198415 Diehr, 198415 Diehr, 198415

Concurrent medical conditions

Dementia

Immunosuppression Asthma

GG8 G24 GG8

G98 G89 G24

34 22 G1G

G85 38

Heckerling, 199018 Heckerling, 199018 Heckerling, 199018

LR, likelihood ratio.

sputum production (+ 1 point); respiratory rate > 25 breaths per minute (+ 2 points); and temperature > 37-8°C (100°F)(+ 2 points). Patients who had a score of - 1 or greater were considered to have pneumonia. A threshold score of - 1 was associated with a positive likelihood ratio (+ LR) of 1-5 and a negative likelihood ratio (- LR) of 0-22. A threshold score of + 1 was associated with a + LR of 5-0 and a - LR of 0-47, while a threshold score of + 3 had a + LR of 14-0 and a - LR of 0-82.

Singal et al1 estimated the probability of CAP based on the following formula:

where Y = - 3-095 + (1-214, if cough present) + (1-007, if fever present) + (0-823, if crackles present). Heckerling et al.18 estimated the probability of pneumonia by first determining how many of the following five findings were present:

• absence of asthma

• decreased breath sounds

The number of findings in combination with the prevalence (i.e. pretest probability) of pneumonia could then be applied to a nomogram provided by Heckerling et al.18 to determine the post-test probability of pneumonia. The prediction rule by Heckerling et al.18 demonstrated a receiver operating characteristic (ROC) area of 0-82 in the derivation cohort and ROC areas of 0-82 and 0-76 in the two validation cohorts. Gennis et al.6

Table 6.2 Diagnosing community-acquired pheumonia from physical examination

Sensitivity Specificity Positive LR Negative LR Reference

Vital signs

Table 6.2 Diagnosing community-acquired pheumonia from physical examination

Vital signs

Temperature > 37 8 °C (100 °F)

027

094

44

078

Diehr, 198415

045

0*81

24

0 68

Singal, 198917

055

077

24

0 58

Heckerling, 199018

067

052

14

0 63

Gennis, 198816

RR > 30

029

089

26

0 80

Gennis, 198816

RR > 25

029

092

34

078

Diehr, 198415

040

074

15

0 82

Heckerling, 199018

RR > 20

076

037

12

0 66

Gennis, 198816

HR > 120

021

089

19

0 89

Gennis, 198816

HR > 100

065

072

23

0 49

Heckerling, 199018

050

069

16

073

Gennis, 198816

Any abnormal VS

097

020

12

018

Gennis, 198816

Lung examination

Asymmetric respirations

004

100

0 96

Diehr, 198415

Egophony

004

0995

86

0 96

Diehr, 198415

028

095

53

076

Heckerling, 199018

008

097

20

0 96

Gennis, 198816

Dullness to percussion

026

094

43

079

Heckerling, 199018

012

095

22

0 93

Gennis, 198816

Bronchial BS

013

096

35

0 90

Heckerling, 199018

Crackles

019

093

27

0 87

Diehr, 198415

050

0*81

26

0 62

Heckerling, 199018

0*41

076

17

078

Singal, 198917

035

078

16

0 83

Gennis, 198816

Decreased BS

049

0*81

25

0 64

Heckerling, 199018

033

086

23

078

Gennis, 198816

Rhonchi

035

077

15

0 85

Gennis, 198816

053

063

14

076

Heckerling, 199018

Any chest finding

077

041

13

0 57

Gennis, 198816

BS, breath sound; HR, heart rate; LR, likelihood ratio; RR, respiratory rate; T, temperature; VS, vital sign.

BS, breath sound; HR, heart rate; LR, likelihood ratio; RR, respiratory rate; T, temperature; VS, vital sign.

suggested that chest radiographs should be obtained if one or more of the following vital sign abnormalities was present: respiratory rate > 30 breaths per minute, heart rate > 100 beats per minute, and temperature > 37-8°C (100°F). The presence of any these vital sign abnormalities was associated with a + LR of 1-2. The absence of all of these vital sign abnormalities was associated with a - LR of 0-18 for diagnosing pneumonia.

A national survey identified that 5% of patients with cough have pneumonia.20 If we assumed that, prior to obtaining history, physical examination, or any other lab tests, the pretest probability of pneumonia for our patient was 5%, and we applied the above prediction rules to our patient, then the Diehr rule15 would have suggested that our patient had a probability of CAP of 42%; the Singal rule17 would have predicted a probability of 1/(1 +e0874) = 1/(1 + 2 - 7 1 8 2 80874) = 1/(1 + 2-396477618) = 29%; the Heckerling rule18 a probability of 3%, and the Gennis rule a probability of 6%. Thus, we are unable to make the diagnosis of pneumonia based solely on history and physical examination.

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Coping with Asthma

Coping with Asthma

If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.

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