Utility of C‐reactive protein and serum amyloid A in the diagnosis of equine protozoal myeloencephalitis

Abstract

BackgroundAccurate antemortem EPM diagnosis requires evidence of intrathecal antibody production. Some advocate the use of acute phase proteins in addition to serology, which alone results in substantial false positives.Hypothesis/ObjectivesThe purpose of this study was to determine if serum C‐reactive protein (CRP) or serum amyloid A (SAA) concentrations were elevated in cases of equine protozoal myeloencephalitis (EPM) compared to other neurological diseases.Animals25 clinical cases of equine neurological disease: EPM (10), cervical vertebral stenotic myelopathy (CVSM) (10), neuroborreliosis (2), equine motor neuron disease (1), degenerative myelopathy (1), and leukoencephalomalacia (1).MethodsSerum and CSF CRP and SAA were measured. Selection criteria included neurologic disease, antemortem diagnosis of EPM or CVSM, or postmortem diagnosis of EPM, CVSM, or other neurologic disease, and availability of serological results and archived samples for testing.ResultsSerum SAA and serum CRP levels were generally undetectable or low in horses with EPM (median CRP ≤0.1 mg/L, ≤0.1‐14.4 mg/L; median SAA ≤0.1 mg/L, ≤0.1‐6.11 mg/L) and CVSM (median CRP ≤0.1, ≤0.1‐2.41 mg/L; median SAA ≤0.1mg/L, ≤0.1‐13.88 mg/L). CSF CRP and SAA for horses with EPM (median CRP 3.35 mg/l, 0.19‐13.43 mg/l; median SAA ≤0.1 mg/L, ≤0.1‐2.4 mg/L) and CVSM (median CRP 4.015 mg/L, 0.16‐9.62 mg/L; median SAA 0.62 mg/L, ≤0.1‐2.91 mg/L) were also undetectable or low. Kruskal–Wallis test showed no statistically significant differences between serum CRP (P = .14), serum SAA (P = .79), spinal fluid CRP (P = .65), or spinal fluid SAA between horses with EPM and CVSM (P = .52).ConclusionNeither SAA nor CRP in serum or CSF aid diagnosis of EPM.

A comprehensive and comparative proteomic analysis of horse serum proteins in colitis

“…Previous studies reported that horse colic caused the increase in SAA concentrations in serum, 11,21,22 and the concentrations of SAA and CRP were increased in sera of horses with protozoal myeloencephalitis. 10 Based on the quantitative results of our study, CRP and haptoglobin did not show any significant increase (P ≥ .05) in accordance with the previous studies. In contrast, SAA showed a significant increase, although it did not meet the criteria for identification owing to the lack of unique peptides.…”

“…[5][6][7] Changes in the concentrations of these serum proteins reflect the degree of inflammation in horses and therefore, these serum proteins are used to evaluate the disease state of horses in veterinary medicine. [8][9][10] For the measurement of serum protein concentrations, enzyme-linked immunosorbent assay (ELISA) is the most commonly used method due to its high sensitivity, efficiency and reproducibility. [11][12][13] However, there is a possibility of false-positive reactions caused by the cross-reactivity of antibody.…”

Equine Inflammatory Markers in the Twenty-First Century

“…A retrospective study assessed the usefulness of SAA in the diagnosis of equine protozoal myeloencephalitis using stored serum or cerebrospinal fluid samples from 25 clinical cases. 88 Affected horses had low or undetectable SAA concentrations in both sample types, indicating that SAA measurement is unlikely to aid in a clinical diagnosis of this disease.…”

Biomarkers in Stress Related Diseases/Disorders: Diagnostic, Prognostic, and Therapeutic Values

“…APPs are normally secreted under the influence of innate immunity or stress and whose concentrations change upon secretory stimuli. The serum concentrations of positive APPs, such as C-reactive proteins (CRP) and serum amyloid A (SAA), are elevated significantly in response to infections and inflammations (Mittelman et al, 2018). While the serum concentrations of negative APPs, such as albumin and transferrin, decrease in response to infection, inflammation, and stress (Cray et al, 2009).…”