Prevalence of idiopathically elevated ESR and CRP in patients undergoing primary total knee arthroplasty as a function of body mass index

Abstract

Background: Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are commonly used inflammatory markers utilized to aid in the diagnosis of periprosthetic infection (PJI). Patients with obesity, however, are known to have elevated baseline levels of these inflammatory markers. Therefore, this retrospective study aimed to determine the relationship between elevated ESR and CRP and body mass index (BMI) in patients undergoing total knee arthroplasty (TKA). In doing so, physicians can better determine whether BMI should be taken into account when evaluating the prognostic value of elevated preoperative ESR and CRP levels for risk of PJI in primary TKA patients. Methods: This is a retrospective case series of 181 patients who had undergone primary TKA at a single institution. Patients undergoing primary unilateral TKA were eligible unless they had undergone previous TKA, contralateral knee symptoms, or elevated white blood cell (WBC) count. A linear regression model was utilized to demonstrate the relationship between proportions of patients with elevated biomarker values and categories of BMI. Analysis of variance and independent two-sample t-tests were utilized to assess differences in mean ESR, CRP, and WBC levels between the "healthy patients" and "patients with comorbidities" subgroups within each BMI category. Results: Eligible patients (n ¼ 181) were stratified by BMI category. Elevated ESR was associated significantly with BMI (ESR: r 2 ¼ 0.89, P < 0.001) unlike elevated CRP (r 2 ¼ 0.82, P ¼ 0.133) and WBC count (r 2 ¼ .01; P ¼ .626). No statistically significant differences in ESR values and WBC count between the "healthy patients" versus "patients with comorbidities" were demonstrated within any BMI category. In patients of normal weight (BMI 20e25 kg/m 2 ), "healthy patients" had a statistically significantly higher mean CRP level than "patients with comorbidities" (1.73 mg/L vs. 0.70 mg/L, P < 0.001). There were no other statistically significant differences in mean CRP levels by health status. Conclusion: Caution is advised when utilizing ESR and CRP to diagnose periprosthetic joint infection without considering BMI given that increasing preoperative levels of ESR and CRP are correlated with higher BMI.

The Use of Preoperative CRP and ESR as Predictive Markers of Prosthetic Joint Infection in Primary Total Hip and Knee Arthroplasty

“…A publication by Watson, et al looked specifically at idiopathically elevated CRP and ESR in patients undergoing primary TKA. They found that higher BMI was correlated with higher levels of preoperative CRP and ESR [33]. Our study supports this same finding; patients with BMI in the obese category (> 30), were more likely to have elevated preoperative CRP level (OR 4.2, p < 0.0001).…”

Moderately elevated erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) in patients with no clinical signs or symptoms of infection is not a contraindication for total knee arthroplasty: a retrospective cohort study

“…Although elevation of ESR or CRP in patients without clinical signs and symptoms of infection is considered an idiopathic elevation, recent studies suggest significant associations between the patients’ characteristics and elevation of inflammatory markers such as ESR and CRP. In this respect, elevated levels of ESR and CRP have been shown to be more prevalent in patients with higher BMI 19. Similarly, the mean BMI of the patients was significantly more in patients with idiopathic ESR elevation in the present study.…”

“…In this respect, elevated levels of ESR and CRP have been shown to be more prevalent in patients with higher BMI. 19 Similarly, the mean BMI of the patients was significantly more in patients with idiopathic ESR elevation in the present study. These observations do not support the routine evaluation of ESR as part of the preoperative planning for elective TKA, as obesity is prevalent in patients who are TKA candidates.…”

Preoperative Risk Factors for Periprosthetic Joint Infection: A Narrative Review of the Literature

“…This association held true regardless of other associated risk factors, such as smoking, obesity, and diabetes [87]. Contrastingly, in another study involving a sample of 351 patients undergoing their first knee implantation by a single surgeon, no statistically significant difference was found between the risk of PJI and preoperative CRP and ESR levels [88]. One reason for this heterogeneity might be that ESR and CRP can be elevated in various conditions, while multiple factors are considered as predisposing the development of PJI independent of inflammation index values.…”