Elsevier

The Veterinary Journal

Volume 166, Issue 3, November 2003, Pages 233-237
The Veterinary Journal

Critical differences of acute phase proteins in canine serum samples

https://doi.org/10.1016/S1090-0233(02)00315-5Get rights and content

Abstract

The critical difference values for acute phase proteins in canine serum samples were established on a week-to-week basis. Blood samples from 11 apparently clinically healthy dogs were collected once weekly for five consecutive weeks. For each protein the total variance of analytical results was divided into intraindividual variance (SIntra2), interindividual variance (SInter2), and analytical variance (SAnalytical2). The critical difference (dK) was then calculated as dk=22(SIntra2+SAnalytical2). The critical difference values were 1.95 g/L for haptoglobin, 4.85 mg/L for C-reactive protein, and 0.016 ΔAbs/min for ceruloplasmin.

When used in conjunction with the corresponding reference interval, critical difference values can be an aid in correctly interpreting acute phase protein results, by determining whether observed differences between two consecutive measurements in individual animals are due to natural variation or due to disease therapy or experimental procedures.

Introduction

Acute phase proteins (APP) such as haptoglobin, ceruloplasmin, and C-reactive protein (CRP) are plasma proteins that increase in concentration following tissue damage caused by inflammation, infection or trauma. Investigations over the last decade have shown that the quantification of APP concentration in plasma or serum can provide valuable diagnostic information in the detection, prognosis, and monitoring of disease (Eckersall, 2000).

In the dog, levels of APP have been reported to increase in many infections and inflammatory conditions such as surgical trauma (Conner et al., 1988), leishmaniasis (Martı́nez-Subiela et al., 2002), and polyarthritis (Eckersall et al., 1999) and an APP assay could be used as a rapid screening test for inflammation, providing better sensitivity compared with other traditional inflammatory markers such as leukocytosis and neutrophilia (Solter et al., 1991).

Frequently, concentrations of APP present in the serum of an animal are compared with a population-based reference range derived from an observed distribution of measurements of the parameter in an appropriate group of animals and containing the central 95% of the distribution. An analytical result outside this reference interval classifies the animal as abnormal indicating an unusual or pathological condition. However other ways of assessment such as the critical difference (dk) may be used, in which the patient serves as its own reference using a comparison of analytical results from samples obtained serially at appropriate intervals. The critical difference allows consecutive analytical results to be compared (Stamm, 1982; Costongs et al., 1985) and assists in determining whether the difference between two consecutive results can be safely ascribed to natural variation or whether it is caused by others factors such as disease, therapy or experimental procedures.

The present study was designed to establish the critical difference values for acute phase proteins concentrations in canine serum samples in a week-to-week basis. Such data have not been reported previously.

Section snippets

Animals

Eleven German-Braco dogs, six males and five females, aged five to six years, were included in the study. They were apparently clinically healthy prior to and during the study, presenting no abnormal findings at physical examination, and routine haematological and biochemical test results were within reference ranges established by the Clinical Pathology Laboratory at Murcia Veterinary School. All dogs belonged to the Murcia University Animal Resources Centre and were housed in the Centre’s

Results

The K–S test indicated that all the data were distributed in a Gaussian manner. Fig. 1, Fig. 2, Fig. 3 show the means and absolute ranges of serum haptoglobin, CRP, and ceruloplasmin concentrations of the healthy dogs in the course of the 5 weeks. The mean±2 SD concentrations of haptoglobin varied between a minimum of 0.2±0.14 g/L and a maximum of 1.56±0.56 g/L. For CRP the mean concentrations ±2 SD were between 0.2±0.41 and 1.89±2.30 mg/L; and for ceruloplasmin the mean ±2 SD absorbance values

Discussion

Elevated acute phase protein levels occur early in a variety of infectious and inflammatory diseases, remain high throughout the infection, and decrease in response to treatment (Martinez-Subiela et al., 2001b). The rapid rise in APP concentration after tissue injury makes them useful markers of inflammation in clinical diagnosis and prognosis and when monitoring treatment (Duthie and Eckersall, 2001).

Interpretation of analytical results from APP analysis in veterinary medicine is commonly

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