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British Journal of Healthcare and Medical Research - Vol. 10, No. 3
Publication Date: June 25, 2023
DOI:10.14738/bjhmr.103.14900
Carroll, M. B. (2023). Impact of BMI on Erythrocyte Sedimentation Rate and C-Reactive Protein in Patients Without a Rheumatic
Autoimmune Disorder: A Medical Record Analysis. British Journal of Healthcare and Medical Research, Vol - 10(3). 291-302.
Services for Science and Education – United Kingdom
Impact of BMI on Erythrocyte Sedimentation Rate and C-Reactive
Protein in Patients Without a Rheumatic Autoimmune Disorder:
A Medical Record Analysis
Matthew B. Carroll
Bienville Boulevard, Ocean Springs, MS 39564
ABSTRACT
Objective: Obesity is an inflammatory condition associated with arthralgias.
Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP) measure
systemic inflammation. Increasing body mass index (BMI) could increase ESR and
CRP in patients with nonspecific arthralgias. Methods: Medical record analysis of
1,185 clinic encounters was performed. Relationship between BMI with ESR and
CRP and differences compared among three groups (Group 1: BMI ≤ 29.9 kg/m2,
Group 2: BMI ≥ 30.0 kg/m2 but ≤ 39.9 kg/m2, and Group 3: BMI ≥ 40.0 kg/m2).
Results: Mean age 56.8 (± 14.1) years with a female predominance (82.2%) and age
50 years (71.2%). Weak positive correlation with ESR (r = 0.147, p < 0.0001) with
no relationship with CRP (r = 0.042, p = 0.151). Relationship with ESR stronger for
age under 50, female gender, and Caucasian ethnicity. Relationship with CRP
stronger for age under 50, female gender. Mean ESR higher in Group 3 (37.9 (95%
Confidence Interval (CI) 35.4 – 40.5) mm/hr). Mean CRP in Group 3 (2.00 (95% CI
1.82 – 2.19) mg/dL) higher than Group 2 but not Group 1. Group 3 mean ESR higher
for age under 50, female gender, Caucasian ethnicity. Group 3 mean CRP higher for
female gender. Conclusion: Positive correlation between BMI and ESR noted. Mean
ESR and CRP higher for Group 3. For ESR, age under 50, female gender, and
Caucasian ancestry demonstrated statistically significant differences for Group 3.
For CRP, only female gender higher for Group 3.
Keywords: Body Mass Index, Erythrocyte Sedimentation Rate, C-Reactive Protein,
Inflammation, BMI: Body Mass Index, ESR: Erythrocyte Sedimentation Rate, CRP: C- Reactive Protein, SLE: Systemic lupus erythematosus, RA: Rheumatoid arthritis,
SSc: Systemic sclerosis, CI: Confidence Interval.
INTRODUCTION
The erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are two established
serologic biomarkers that measure levels of inflammation. They measure different acute phase
reactants, the ESR indirectly measuring fibrinogen, and CRP measuring the protein directly, as
they change in response to infectious or inflammatory events. They can aide the clinician in the
diagnosis of various types of inflammatory arthritis but also help monitor various infectious or
inflammatory conditions. Rheumatologists rely on these tests to help rule in or potential
exclude conditions (such as Polymyalgia Rheumatica) while also using them to measure disease
activity and response to medications.[1] Though relatively inexpensive and quick turnaround
time are strengths of the ESR and CRP, they lack consistent sensitivity or specificity as their
performance will vary with various acute and chronic inflammatory conditions.[2] ESR and CRP
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British Journal of Healthcare and Medical Research (BJHMR) Vol 10, Issue 3, June- 2023
Services for Science and Education – United Kingdom
values also vary with age, gender, and ethnicity. It has been established that low-grade CRP
elevation is associated with various metabolic stressors such atherosclerosis, obesity, type 2
diabetes, sedentary lifestyles, an unhealthy diet, and even being unmarried. [3, 4] CRP levels
vary with age, sex, and ethnicity, though less so than ESR levels [2]. Obesity is defined as a body
mass index (BMI) greater than 30 kg/m2. BMI is a measure of body fat based on height and
weight, calculated as a person's weight in kilograms divided by the square of their height in
meters. In the last 3 decades, the worldwide prevalence of obesity has increased 27.5% for
adults.[5] Obesity and pain are common problems affecting the older adult and a possible
relationship between the two is considered.[6] Cross-sectional studies have revealed a high
correlation between pain and obesity and a few longitudinal studies implicate obesity as a risk
factor for the development of pain and the associated reduction in quality of life.[6] Obesity
related pain arises from mechanical stress as well as metabolic disruptions, and mitigating
obesity may help reduce the risk of developing pain and improve recovery from pain.[6, 7]
Rheumatic autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid
arthritis (RA), and systemic sclerosis (SSc) are illnesses characterized by systemic
inflammation. A host of genetic and environmental factors over time lead to dysregulation of
the immune system and subsequent inflammation and damage of target organs. Tissues such
as cartilage, joint synovium, and skin are most frequently targeted.[8] When considered
together, rheumatic autoimmune diseases are estimated to afflict more than 7% of the general
population.[9] While rheumatic autoimmune diseases can occur across the lifespan, the typical
presentation occurs in mid- or late- adulthood,[8, 10] and these diseases are much more
common in women than in men, with approximately 90 % of prevalent cases being female for
SLE and SSc, and approximately 75 % for RA.[11]. The variability in the sensitivity and
specificity of the ESR and CRP, the impact that obesity has on inflammatory markers such as
CRP, and the symptoms of rheumatic autoimmune diseases (and differential impact on
women), create a “perfect storm” that significantly impacts the decision making of clinicians
across the spectrum of care. As an example, an obese patient presenting to her primary care
provider with arthralgias and prolonged morning stiffness could have a rheumatic autoimmune
illness, fibromyalgia, pain from the mechanical and metabolic disturbances of her obesity, or a
host of other conditions. In the absence of other more sensitivity and/or specific serologic
biomarkers, an ESR and CRP likely will be ordered. If these results return mildly elevated, with
an ESR of 25 mm/hr and CRP of 1.5 mg/dL, this might prompt concern for a rheumatic
autoimmune disease and a referral to Rheumatology for further evaluation and possible
treatment. In light of the current (and projected) Rheumatology workforce shortage,[12] initial
evaluation may be delayed for months, or even up to a year. The purpose of this study was to
explore the relationship between BMI to that of ESR and CRP for patients evaluated at a
community hospital rheumatology clinic as well as to identify differences in demographic
factors that would distinguish when the ESR and CRP were likely impacted by groups of
patients based on their BMI and not an infectious or inflammatory process.
METHODS
A medical records review of patient encounters from a Rheumatologist practicing as an
employee in a community hospital system were reviewed from 1 July 2017 to 30 June 2022.
The hospital system serves about 250,000 people in a suburban/rural area in the southeast US.
The Rheumatology Clinic is a referral only clinic. At each encounter patients underwent a
reasonably thorough history and physical examination as well as had vital signs and serologic
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Carroll, M. B. (2023). Impact of BMI on Erythrocyte Sedimentation Rate and C-Reactive Protein in Patients Without a Rheumatic Autoimmune
Disorder: A Medical Record Analysis. British Journal of Healthcare and Medical Research, Vol - 10(3). 291-302.
URL: http://dx.doi.org/10.14738/bjhmr.103.14900
or radiographic testing ordered appropriate for their health at the time of the interview. Data
collected from these medical encounters for this study included the date of the encounter,
patient age, reported gender, reported ethnicity, primary diagnosis for the encounter,
secondary and additional diagnoses when available, BMI, ESR, and CRP. ESR and CRP were
measured using standard laboratory techniques. Patient could have multiple encounters with
the physician at different points in time. The initial data request yielded 14,253 records. These
records were then filtered based on diagnosis, with diagnoses of an inflammatory arthritis
(such as RA, SLE, Psoriatic Arthritis, infectious arthritis, etc.) or inflammatory condition (such
as Polymyalgia Rheumatica) excluded. Primary diagnoses that were accepted included but
were not limited to osteoarthritis, positive anti-nuclear antibody or positive rheumatoid factor
(not associated with a rheumatic autoimmune disease or other etiology such as infection,
malignancy, etc.), and benign joint hypermobility syndrome. After this filter was applied, 6,069
records remained. Next, a filter limiting ESR values to 0 – 150 mm/hr (values such as “<0”,
>150”, or “NULL” were excluded) left 2,845 records for review. Another filter limiting CRP to
values between 0 and 28 mg/dL was applied (values such as “NULL” were excluded). This left
1,220 records. The final filter applied was for a recorded BMI. This ultimately left 1,185 records
for statistical analysis. A flow chart of this process is detailed in Figure 1.
Figure 1: Flow Chart of record exclusion
Key: BMI = Body Mass Index; ESR = Erythrocyte Sedimentation Rate, CRP = C-Reactive Protein
The hypothesis of this study was that a (positive) relationship would be identified between BMI
and ESR and CRP but that there would be differences among different groups of BMI based on
various demographic categorization. Thus, this study had two endpoints. First, assess the
strength of the relationship between BMI with ESR and/or CRP. As noted, a positive
relationship was expected as this has been described elsewhere.[1] Second, after dividing the