Evaluation of the immunocrit method to detect failure of passively acquired immunity in dairy calves

Kimberly A. Thompson, Marie C. Rayburn, Munashe Chigerwe

Research output: Contribution to journalArticle

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Abstract

OBJECTIVE To evaluate the usefulness of serum immunocrit measurement to detect failure of passively acquired immunity (FPI) in dairy calves. DESIGN Diagnostic test evaluation. ANIMALS 249 female dairy calves (age, 2 to 6 days). PROCEDURES A blood sample was collected from each calf, and serum was harvested. Immunocrit was measured in serum samples by use of 55% ammonium sulfate solution and the standard technique. Serum IgG concentration was measured by means of radial immunodiffusion (reference standard), with FPI defined as a result < 1,000 mg/dL. The immunocrit value (cutpoint) that maximized both sensitivity and specificity of the method for detection of FPI was determined by construction of receiver operating characteristic curves, and likelihood ratios for positive and negative test results were calculated. RESULTS Immunocrit values were significantly correlated (ρ = 0.71) with serum IgG concentration as measured by radial immunodiffusion. An immunocrit cutpoint of 11% was optimal for detection of FPI in the calves. Sensitivity and specificity of the immunocrit method at this cutpoint were 0.88 (95% confidence interval [CI], 0.79 to 0.97) and 0.51 (95% CI, 0.44 to 0.58), respectively. Likelihood ratios for positive and negative test results were 1.80 (95% CI, 1.51 to 2.14) and 0.23 (95% CI, 0.11 to 0.51), respectively. CONCLUSIONS AND CLINICAL RELEVANCE The immunocrit method was useful for identifying dairy calves with FPI and was simple and could be quickly performed. Because precipitation of immunoglobulins by ammonium sulfate is not species specific, the immunocrit method should be evaluated for detection of FPI in other veterinary species as well.

Original languageEnglish (US)
Pages (from-to)702-705
Number of pages4
JournalJournal of the American Veterinary Medical Association
Volume251
Issue number6
DOIs
StatePublished - Sep 15 2017

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dairy calves
Adaptive Immunity
blood serum
confidence interval
Confidence Intervals
Serum
Immunodiffusion
Ammonium Sulfate
ammonium sulfate
Immunoglobulin G
methodology
calves
Sensitivity and Specificity
reference standards
Routine Diagnostic Tests
ROC Curve
diagnostic techniques
immunoglobulins
adaptive immunity
Immunoglobulins

ASJC Scopus subject areas

  • veterinary(all)

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Evaluation of the immunocrit method to detect failure of passively acquired immunity in dairy calves. / Thompson, Kimberly A.; Rayburn, Marie C.; Chigerwe, Munashe.

In: Journal of the American Veterinary Medical Association, Vol. 251, No. 6, 15.09.2017, p. 702-705.

Research output: Contribution to journalArticle

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abstract = "OBJECTIVE To evaluate the usefulness of serum immunocrit measurement to detect failure of passively acquired immunity (FPI) in dairy calves. DESIGN Diagnostic test evaluation. ANIMALS 249 female dairy calves (age, 2 to 6 days). PROCEDURES A blood sample was collected from each calf, and serum was harvested. Immunocrit was measured in serum samples by use of 55{\%} ammonium sulfate solution and the standard technique. Serum IgG concentration was measured by means of radial immunodiffusion (reference standard), with FPI defined as a result < 1,000 mg/dL. The immunocrit value (cutpoint) that maximized both sensitivity and specificity of the method for detection of FPI was determined by construction of receiver operating characteristic curves, and likelihood ratios for positive and negative test results were calculated. RESULTS Immunocrit values were significantly correlated (ρ = 0.71) with serum IgG concentration as measured by radial immunodiffusion. An immunocrit cutpoint of 11{\%} was optimal for detection of FPI in the calves. Sensitivity and specificity of the immunocrit method at this cutpoint were 0.88 (95{\%} confidence interval [CI], 0.79 to 0.97) and 0.51 (95{\%} CI, 0.44 to 0.58), respectively. Likelihood ratios for positive and negative test results were 1.80 (95{\%} CI, 1.51 to 2.14) and 0.23 (95{\%} CI, 0.11 to 0.51), respectively. CONCLUSIONS AND CLINICAL RELEVANCE The immunocrit method was useful for identifying dairy calves with FPI and was simple and could be quickly performed. Because precipitation of immunoglobulins by ammonium sulfate is not species specific, the immunocrit method should be evaluated for detection of FPI in other veterinary species as well.",
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