Serum Inflammatory Markers in the Diagnosis of
Diabetic Foot Osteomyelitis: A Meta-Analytic Review
Adam Fleischer, DPM, MPH, Maureen Allanson, BS, James Wrobel, DPM, MS
Department of Surgery, Advocate Illinois Masonic Medical Center
Abstract:
Introduction: The aim of this meta-analytic review was to help establish optimal
cut-off levels when using erythrocyte sedimentation rate (ESR) and Creactive protein (CRP) in the diagnosis of diabetic foot osteomyelitis (OM).
A secondary aim was to determine whether these simple diagnostic tests
demonstrate more of a “threshold effect” or “dose-response” when
discriminating between patients with and without OM.
Methods: Six eligible articles were identified through a search of Medline and
EMBASE electronic databases from 1966 to 2010. Summary likelihood
ratios for predicting the presence of OM in the case of both a positive test
result (LR+, sensitivity/1-specificity) and negative test result (LR-, 1sensitivity/specificity) were calculated along with 95% confidence intervals
(CIs) using random-effects models for several commonly reported
thresholds for ESR and CRP. Mantel-Haenszel test was used to test for
dose-response as thresholds were increased given a positive result (LR+)
and decreased for a negative result (LR-).
Results/Conclusion: ESR > 80mm/h proved to be the best threshold and test
for ruling in OM (LR+ 9.40 [95% CI 0.65 - 135). Furthermore, there was an
obvious dose-response with increasing ESR levels, and a three-fold
increase in the likelihood of OM as ESR levels increased from 60mm/h to
80mm/h (p = 0.04). CRP ≤ 3.2mg/dl proved to be the best blood test for
ruling out OM (LR- 0.23 [95% CI 0.17-0.52]), however, unlike ESR, CRP
demonstrated more of a threshold effect in the diagnosis of OM as
increasing and decreasing levels did not appear to alter the likelihood of
having underlying OM significantly (p > 0.05).

Articles were included for review if they fulfilled all of the following criteria:



Data could be extracted into 2x2 tables

The diagnostic test was compared with a reference standard.
There were a total of 305 patients represented in this meta-analysis.

The majority of these people were inpatients with a mean prevalence of OM of
59%.
Table 1. Studies Describing CRP or ESR in the Diagnosis of
Lower Extremity Osteomyelitis in Patients with Diabetes
Mellitus
In studies that included patients with and without DM, only those patients with
DM were included in the analysis.

Summary likelihood ratios for predicting the presence of OM in the case of both a
positive test result and negative test result, as well as sensitivities and
specificities were calculated using random-effects models for several commonly
reported thresholds for ESR and CRP.

The Mantel-Haenszel test for trend was used to test for dose-response as
thresholds were increased given a positive result and decreased for a negative
result.

P values less than 0.5 were considered significant.

All analyses were performed using SAS version 9.2 for Windows.
Malabu et
al 2007
Results:
Introduction:

Our original search yielded 152 potential articles of which 19 were selected for
review by the authors. Fourteen articles were excluded: 9 articles did not use
ESR or CRP in the diagnosis of osteomyelitis and the data could not be
extracted in the remaining 5. Our reference search provided us with an additional
35 articles; however only 1 of these articles fulfilled all of the inclusion criteria
mentioned previously.
NS
Ertugrul
et al 2009
II
Prospe
ctive
Yes
III
Retros
pective
No
56.3
54
0
61.0
69
100
Pathology or radiographs or
Technitium-99 three phase bone
scans
64.0
52
54
Histopathology or microbiological
culture or T1 weighted MRI scan
100
Histopathology (focal necrosis or
intramedullary fibrosis with
infiltration of neutrophils)
61.5
63
resonance imaging, NS, Not specified, OM, osteomyelitis
*Level I: independent, blind evaluation of test with gold standard among a large sample of consecutive patients
with suspected target condition.. Level II: independent, blind evaluation of test with gold standard among a
small sample of consecutive patients with suspected target condition. Level III: nonindependent, blind
evaluation of test with gold standard among a nonconsecutive group of patients with suspected condition.
Level IV: nonindependent evaluation of test with standard of uncertain validity among a sample of patients
who have the target condition. Level V: nonindependent evaluation of test with standard of uncertain validity
among a sample of patients
† Calculations based on number of ulcers


Methods:
Figure 1. Search strategy

All six articles examined ESR’s relation to diabetic osteomyelitis however, only
one article, Fleischer et al 2009, described CRP thresholds.
The search was limited to studies involving adults and English language
articles from the period 1966 through 27 June 2010.

The articles we examined were of fair to poor quality generally.

Two-thirds of the studies were prospective.
We identified additional articles through a hand search of references from
retrieved articles, previous reviews, and polling experts. The titles and
abstracts of the articles retrieved were evaluated to determine their eligibility
for our review. Publications in abstract and letter form were included to
minimize publication bias.

None of the article displayed level one evidence and only two studies reported
consecutive patient enrollment.

All but one of the studies used bone histopathology to diagnose osteomyelitis;
however, Kaleta et al and Ertrugal et al utilized the histopathology goldstandard inconsistently at about 55% of the time.
ESR > 80mm/h was identified as the single most specific laboratory test for
diagnosing OM (spec=94.2%). There was an obvious dose-response observed
for the likelihood of underlying OM with increasing ESR thresholds, and a
three-fold increase in the likelihood of OM as ESR threshold was increased
from 70mm/h to 80mm/h (3.11 -> 9.40).
This trend was statistically significant using the Mantel-Hanszel test with a p
value of 0.04 (Table 2).
Table 2. Summary Characteristics for Erythrocyte
Sedimentation Rate for Diagnosing Osteomyelitis
ESR threshold n
Sensitivity
Specificity
>60 mm/h
129 80.5 (74.0-85.8) 73.1 (63.4-80.9)
>70 mm/h
267 64.7 (60.6-68.0) 82.5 (75.3-88.2)
>80 mm/h
129 62.3 (56.8-64.9) 94.2 (86.1-98.0)
Search strategy

III
Prospe
ctive
NS
Positive results of two imaging
modalities (bone scan, MRI,
radiographs) or positive probe to
bone
Table 1. Abbreviations: CRP, C-reactive protein, ESR, Erythrocyte sedimentation rate, MRI, magnetic
To better characterize how ESR and CRP might be used in the diagnosis of
diabetic foot OM.

Rabjohn
et al 2007
Fleischer
et al 2009
Purpose
We searched MEDLINE and EMBASE databases with the following search
terms: “diabetic” and “osteomyelitis” or “diabetic” and “ulcer”, in addition to
each of the following words: C-reactive protein and erythrocyte sedimentation
rate.
Prospe
ctive
In total, six articles were included in our meta-analysis (Figure 1).
Diabetes mellitus (DM) is a significant public health concern, with an estimated
23.6 million people affected in the US alone. The US spends approx. $174
billion, or ~1 out of every 5 healthcare dollars, on patients with diabetes annually.
Foot-related complications in the form of ulceration and infection are the leading
cause of hospitalization and lower extremity amputation (LEA) in patients with
diabetes, costing the US healthcare system $43,000 to $63,000 per event. Early
recognition of diabetic OM may curtail the need for LEA, however, confirmatory
tests such as biopsy are invasive. Diagnostic tests such as MRI are expensive
and not always available and standard radiographs lack sufficient sensitivity to
accurately diagnose early OM. Therefore, simple laboratory tests of common
serum inflammatory markers (e.g., ESR, CRP) have been proposed as
diagnostic aids, but there is uncertainty regarding their usefulness in DM OM,
and it is unclear whether or not these tests demonstrate either a dose response
or threshold effect.

IV
Patients
with foot
ulcer
(n=43)
Inpatients
with
clinically
suspected
osteomyeli
tis (n=95)
Inpatients
with
diabetic
foot lesions
(n=46)
Inpatients
with a
single
forefoot
ulceration
(n=54)
LR (+)*
2.89 (0.38-21.5)
3.11 (1.21-7.99)
9.40 (0.65-135)
LR (-)†
0.245 (0.24-2.56)
0.424 (0.178-1.01)
0.365 (0.03-5.26)
Table 2. Data in parentheses represent 95% confidence intervals. Abbreviations: LR (+), positive likelihood
ratio; LR (-), negative likelihood ratio; ESR, erythrocyte sedimentation rate
*Mantel Haenszel test for trend with increasing threshold levels = 4.041, p = 0.044
†Mantel Haenszel test for trend with decreasing threshold levels = 0.636, p = 0.425

Table 3. Summary Characteristics for C-Reactive Protein for
Diagnosing Osteomyelitis
CRP threshold n
Sensitivity
Specificity
2.3 mg/dl
54 88.0 (79.6-94.7)
40.0 (25.3-51.0)
3.2 mg/dl
54 85.3 (75.7-92.2)
65.0 (48.7-76.8)
8.4 mg/dl
54 55.9 (45.9-62.5)
80.0 (63.0-91.3)
LR (+)*
1.47 (0.10-2.84)
2.44 (1.12-3.76)
2.79 (1.51-4.08)
LR (-)†
0.29 (0.21-0.49)
0.23 (0.17-0.52)
0.55 (0.32-1.90)
Table 3. Data in parentheses represent 95% confidence intervals
Level of Study Consecutive
Prevalence of Biopsy,
Source Evidence* Type Enrollment Population Age
OM, %
%
Method of Diagnosis of OM
Inpatients
and
outpatients
Culture and/or pathologic criteria
with foot
(osteonecrosis, marrow fibrosis,
Newman
Prospe
ulcer
and/or presence of inflammatory
et al 1991
II
ctive
Yes
(n=35)
55.0
cells)
68†
100†
Inpatients
with
osteomyeli
Pathology , positive results of at
tis or
least two imaging modalities (bone
Kaleta et
Retros
cellulitis
scan, MRI, radiographs), or positive
al 2001
IV
pective
No
(n=29)
62.0
66
53
probe to bone
Statistical Analysis

Background
They were original studies describing CRP or ESR in the diagnosis of lower
extremity osteomyelitis in patients with DM

Neither increasing nor decreasing levels of CRP demonstrated a dose response
for diagnosing OM as evident by the nonsignifcant Mantel-Haenszel test. CRP
3.2 mg/dl was the best threshold for diagnosing OM with the highest combined
total or sum for sensitivity and specificity of 85.3 and 65.0 respectively.
Abbreviations: LR (+) , positive likelihood ratio; LR (-), negative likelihood ratio; CRP, C-reactive protein
*Mantel Haenszel test for trend with increasing threshold levels = 1.236, p = 0.266
†Mantel Haenszel test for trend with decreasing threshold levels = 1.381, p = 0.240

As CRP threshold (green arrow) for establishing OM is raised from 2.3 to 3.2 to
8.4, the likelihood of getting a true positive compared to a false positive remains
essentially the same, indicating that CRP may demonstrate more of a threshold
effect for diagnosing underlying OM (Figure 2).

However, this is not true of ESR. As the ESR threshold (blue arrow) for
diagnosing OM is increased from 60 to 70 to 80, the likelihood of getting a false
positive decreases significantly as the likelihood of getting a true positive remains
relatively constant. This trend suggests that ESR demonstrates more of a dose
response likelihood of OM with increasing levels (Figure 3).
Figure 2. Summary receiver operating
characteristic curves for CRP (from Fleischer
et al. 2009, unpublished figure, n=54).
Figure 3. Summary receiver operating
characteristic curves for ESR (from Fleischer
et al. 2009, unpublished figure, n=54).
Conclusions:
1. ESR demonstrates a dose-response likelihood of having underlying OM with
increasing levels (p=0.04); however CRP does not show this same pattern
(p=0.266).
2. The likelihood of having OM increased three-fold as the ESR threshold was
increased from 70 mm/h to 80 mm/h.
3. CRP, on the other hand, demonstrates more of a threshold effect in the diagnosis
of OM, with 3.2 mg/dl being the optimal cut-point.
4. ESR appears to be a specific marker for diabetic OM, with increasingly higher
LR+ values at higher threshold levels (p<0.05). An elevated ESR above 80 mm/h
strongly favors the diagnosis of OM (LR+ 9.40).
5. CRP, conversely, appears to be a sensitive marker for diabetic OM, with values
lower than 3.2 effectively ruling out underlying OM (LR- 0.23).
6. Because serum inflammatory markers, by themselves, lack accuracy, we believe
they will be most useful in modulating our pre-test probability for OM prior to
considering our more formal diagnostic (MRI, radiographs) or confirmatory tests
(biopsy/culture).
References:
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Fleischer, AE, Didyk AA, Woods, JB, Burns, SE, Wrobel, JS, Armstrong, DG. Combined clinical and laboratory testing improves diagnostic accuracy for osteomyelitis in the
diabetic foot. J Foot Ankle Surg 48:39-46, 2009.
Kaleta, JL, Fleischli, JW, Reilly, CH. The diagnosis of osteomyelitis in diabetes using erthorcyte sedimentation rate: A pilot study. J Am Pod Med Assoc. 91:445-450, 2001.
Malabu, UH, Al-Rubeaan, KA, Al-Derewish, M. Diabetic foot osteomyelitis: Usefulness of erythrocyte sedimentation rate in its diagnosis. West Afr J Med 26:113-116, 2007.
Newman, LG, Waller J, Palestro, CJ, Schwartz, M, Klein, MJ, Hermann, G, Harrington, E, Harrington, M, Roman, SH, Stagnaro-Green, A. Unsuspected osteomyelitis in
diabetic foot ulcers: Diagnosis and monitoring by leukocyte scanning with indium in 111 oxyquinoline. J Am Med Soc 266:1246-1251, 1991.
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