Transcript Is the lab useful to distinguish Septic Arthritis versus

Is the lab useful to distinguish
Septic Arthritis versus
Transient Synovitis?
Laboratory rounds
Jan 30, 2003
Rob Hall PGY3
Case
 3yo
 What is your
 Refuses to weight bear
differential?
 What tests would you
order?
 How useful are your
tests going to be?
on left hip
 No hx of trauma or
fever
 URTI recently
 T 38.0
 Painful ROM right hip
 Kid looks well
Differential of Limp
 Trauma
– fracture, sprain, strain, contusion, abuse
 Infection
– Septic arthritis, osteomyelitis, cellulitis, fascitis,
myositis
 Inflammation
– Toxic synovitis, JRA, HSP, serum sickness, rheumatic
fever
 Other
– AVN, SCFE, tumor, leukemia, sickle cell
Are a wbc, ESR, or CRP useful for
distinguishing septic arthritis vs transient
synovitis?
 Small retrospective studies with poor design
– Molteni 1978
– McCarthy1980
 Potentially meaningful studies
– Kunnamo 1987
– Del Beccaro 1992
– Kocher 1999
Kunnamo 1987
American Journal of the Diseased Child
 Prospective study of all kids referred to a
tertiary pediatric referral center with
arthritis
 N = 278, only 18 with septic arthritis
 Gold standard was based on follow up if
joint not tapped and no follow up data given
Kunnamo 1987
American Journal of the Diseased Child
 Variable
– CRP > 20
– ESR > 20
– WBC > 12
– T > 38.5
– T>38.5 or
CRP >20
Sensitivity
Specificity
94%
94%
59%
77%
100%
92%
68%
95%
95%
87%
Kunnamo 1987
American Journal of the Diseased Child
 Small study
 Method problems
 Wide confidence intervals
– CRP > 20: sensitivity 94% (95%CI 72 – 99%)
 Doesn’t answer the question
Del Beccaro 1992
Annals of Emergency Medicine
 Retrospective chart review
 Method problems
 N = 132
– Septic arthritis 38
– Transient synovitis 94
 Gold standard problems
– Transient synovitis defined based on clinical
course but 13% lost to follow up
Del Beccaro 1992
Annals of Emergency Medicine
 Statistically significant differences
– Variable Septic Arthritis Transient synovitis
– Temp
38.1
37.2
– ESR
44
19
– WBC
13.2
11.2
Del Beccaro 1992
Annals of Emergency Medicine
VARIABLE
SENSITIVITY
SPECIFICITY
ESR > 20
79%
72%
T > 37.5
66%
68%
T > 38.0
45%
85%
WBC > 15
26%
84%
ESR > 20 and/or 97%
Temp > 37.5
50%
Del Beccaro 1992
Annals of Emergency Medicine
 Wide confidence intervals
 Huge overlap between groups with each
variable
 How can we use this information?
– ESR, CBC, temp not that helpful in isolation
– Combinations may be useful
Kocher 1999
Journal of Bone and Joint Surgery
 Retrospective chart review of 282 patients
 Same metholodogical problems
 Found statistical differences b/w septic arthritis
and transient synovitis for……
–
–
–
–
–
–
Hx of fever
Ability to weight bear
Joint effusion on Xray
Temp
ESR
WBC
Kocher 1999
Journal of Bone and Joint Surgery
 Multivariant analysis found four predictors
of septic arthritis
–
–
–
–
History of fever
Non-weight bearing
ESR > 40
WBC > 12
 Developed an algorithm based on above 4
variables
Kocher 1999
Journal of Bone and Joint Surgery
Predictors
Septic
Arthritis
Group
0%
Probability of
septic arthritis
(%)
0
Transient
Synovitis
Group
22%
1
54
1
3.0%
2
19
14
40%
3
5
53
93%
4
0
30
99.6%
0.2%
Kocher 1999
Journal of Bone and Joint Surgery
 This is NOT a validated prediction rule
 Again suggests that combination of
information is useful
Approach to the Irritable Hip
C o n sid e r th e w h o le p ictu re
H isto ry
P h ys ic a l
X ra y
L ab
F e ver
C h ills
H x of trau m a
F e v er
A b ility to wt b e ar
T e n de rne s s of h ip
L o o ks to xic
Jo int E ffusion
A lte rn a tive dx
ESR
CBC
?CRP
Surprise! The lab alone is NOT
the answer…………
T h e W h o le P ictu re
L o w S u spicion
M o d era te S u sp icion
H ig h S usp icion
N o h x of fever
T < 3 7 .5 , w t b e a rs
E S R < 2 0 , W B C < 12
H x/p h ysica l e qu ivo cal
T > 3 7 .5 o r E S R > 20
o r W B C > 12
F e ver, toxic, d o esn 't
w e igh t b ea r, E S R > 2 0,
W B C > 12
T re at
F o llo w up
C o nsu lt o rtho
T re at an d o b se rve
o r tap
C o nsu lt o rtho
T a p o r dra in ag e in O R