C-Reactive Protein versus Erythrocyte Sedimentation Rate: Implications Among Patients with No Known Inflammatory Conditions

Vanessa Alende-Castro; Manuela Alonso-Sampedro; Carmen Fernández-Merino; Juan Sánchez-Castro; Bernardo Sopeña; Francisco Gude; Arturo Gonzalez-Quintela

doi:10.3122/jabfm.2021.05.210072

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Figure 1.
Boxplot of serum C-reactive protein concentrations in relation to the number of metabolic syndrome criteria. Outliers (values outside 1.5 times the interquartile range above the upper quartile and below the lower quartile) are not represented but are included in the analyses. P value was obtained with the Jonckheere-Terpstra trend test.

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Table 1.

C-Reactive Protein Concentrations According to Demographics, Lifestyle Factors, and Metabolic Abnormalities^*

Factor	N	CRP (mg/dL)	P value
Sex
Female	830	0.14 (0.04–0.42)	Reference
Male	669	0.13 (0.04–0.33)	.186
Age (years)
18–35	295	0.09 (0.03–0.33)	Reference
>35–50	408	0.11 (0.04–0.35)	.033
>50–65	388	0.17 (0.06–0.39)	<.001
>65	408	0.18 (0.06–0.47)	<.001
Alcohol consumption
Abstainers	539	0.16 (0.05–0.46)	Reference
Light drinkers	591	0.11 (0.03–0.33)	<.001
Moderate drinkers	239	0.15 (0.04–0.37)	.146
Heavy drinkers	130	0.17 (0.08–0.43)	.363
Smoking
Never smokers	820	0.15 (0.05–0.41)	Reference
Ex-smokers	388	0.13 (0.04–0.34)	.127
Current smokers	291	0.13 (0.04–0.36)	.183
Physical activity
Low	583	0.16 (0.05–0.46)	Reference
Moderate	548	0.14 (0.04–0.36)	.017
High	368	0.11 (0.04–0.33)	.005
Body mass index
Normal weight	421	0.06 (0.02–0.17)	Reference
Overweight	567	0.13 (0.05–0.36)	<.001
Obesity	511	0.25 (0.10–0.55)	<.001
Metabolic syndrome
No	1191	0.11 (0.04–0.33)	Reference
Yes	308	0.27 (0.12–0.59)	<.001

CRP, C-reactive protein.
↵* Data are medians and interquartile (25^th–75^th percentile) ranges (in brackets). The normal range for serum CRP concentrations is 0–0.5 mg/dL (0–5 mg/L).

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Table 2.

Multivariate Analysis. Linear Regression of C-Reactive Protein (log₁₀-Transformed) in Relation to Demographics, Lifestyle Factors, and Metabolic Factors

Factor	Coefficient (SE)	P value
Sex (male)
Female	Reference	NA
Male	−0.050 (0.035)	.157
Age (years)	0.002 (0.001)	.087
Alcohol consumption
Abstainers	Reference	NA
Light drinkers	−0.114 (0.036)	.001
Moderate drinkers	−0.090 (0.048)	.061
Heavy drinkers	0.013 (0.062)	.829
Smoking
Never smokers	Reference	NA
Ex-smokers	−0.029 (0.038)	.445
Current smokers	0.087 (0.043)	.042
Physical activity
Low	Reference	NA
Moderate	−0.033 (0.035)	.348
High	−0.014 (0.040)	.725
Body mass index (kg/m²)	0.045 (0.003)	<.001
Metabolic syndrome
No	Reference	NA
Yes	0.073 (0.042)	.084
Constant (intercept)	−2.178 (0.107)	NA

CRP, C-reactive protein; NA, not applicable; SE, standard error.
* For the logarithmic transformation, we attributed an arbitrary value of 0.001 mg/dL to patients with undetectable CRP (n = 4).
† All listed covariates were entered into the equation.
‡ Covariates explained 17.4% of the CRP variability (R², 0.174). The body mass index explained 15.7% of the CRP variability.

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Table 3.

Comparison of Demographics, Lifestyle Factors, Metabolic Abnormalities among Categories of Agreement and Discordance between C-Reactive Protein and Erythrocyte Sedimentation Rate Values

Factor	Normal CRP Normal ESR (n = 1123)	High ESR Normal CRP (n = 72)	High CRP Normal ESR (n = 208)	High CRP High ESR (n = 69)
Sex (male)^{^II}	514 (45.8)	30 (41.7)	78 (37.5)^*	33 (47.8)
Age (years)^{^¶}	50 (37–65)	64 (55–74)^{^‡}	55 (42–67)^{^†}	64 (49–76)^{^‡}
Alcohol consumption (g/week)^{^¶}	30 (3–130)	20 (3–85)	10 (3–90)^*	13 (3–140)
Smoking (current)^{^II}	223 (19.9)	12 (16.7)	36 (17.3)	11 (15.9)
Physical activity (low)^{^II}	411 (36.6)	31 (43.1)	91 (43.8)	40 (58.0)^{^‡}
Body mass index (kg/m²)^{^¶}	27.2 (23.9–30.6)	28.1 (25.4–31.7)^*	30.0 (26.2–33.7)^{^‡}	32.0 (27.0–35.6)^{^‡}
Metabolic syndrome (yes)^{^II}	185 (16.5)	24 (33.3)^{^‡}	68 (32.7)^{^‡}	23 (33.3)^{^‡}
Serum IL-6 (pg/mL)^{^¶}	<2 (<2–3.0)	2.2 (<2–4.1)	3.0 (<2–4.9)^{^‡}	4.7 (2.3–8.7)^{^‡}

CRP, C-reactive protein; ESR, erythrocyte sedimentation rate.
↵* P < .05;
↵† P < .01; and
↵‡ P < .001 compared with the reference category (individuals with normal CRP and normal ESR).
^fData available for 1472 individuals.
§ High CRP is defined as >0.5 mg/dL (>5 mg/L); high ESR is defined as >20 mm/h for men and >30 mm/h for women.
↵II Figures for sex, smoking, physical activity, and metabolic syndrome are absolute numbers and percentages (within parentheses).
↵¶ Figures for age, alcohol consumption, body mass index, and serum IL-6 are medians and interquartile ranges (within parentheses).

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Table 4.

Multivariate Analysis (Logistic Regression) of Factors Associated with Discordance between C-Reactive Protein and Erythrocyte Sedimentation Rate^*^{,^†}

	High ESR and normal CRP (n = 72)		High CRP and normal ESR (n = 208)
Factor	OR (95% CI)	P value	OR (95% CI)	P value
Sex (male)	0.815 (0.448–1.481)	.502	0.699 (0.483–1.012)	.058
Age (years)	1.052 (1.034–1.071)	<.001	0.998 (0.988–1.008)	.695
Body mass index (kg/m²)	0.986 (0.930–1.045)	.633	1.099 (1.064–1.136)	<.001

CI, confidence interval; CRP, C-reactive protein; ESR, erythrocyte sedimentation rate; OR, odds ratio.
↵* High CRP is defined as >0.5 mg/dL (>5 mg/L); high ESR is defined as >20 mm/h for men and >30 mm/h for women.
↵† A total of 1472 cases were entered into the equations. The odds ratio (adjusted for all listed variables and alcohol consumption, smoking, metabolic syndrome, and physical activity).