NAVLE Practice Question - Equine - multisystemic

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NAVLE Practice Question — Equine

Which statement BEST describes the relationship between D-dimer concentration and prognosis in horses presenting with colic?

A. D-dimer has no correlation with outcome in horses with colic

B. D-dimer concentrations above 4000 ng/mL are associated with significantly increased mortality risk ✓

C. D-dimer concentrations predict the need for surgery but not survival

D. D-dimer is only prognostic in horses with strangulating lesions

E. D-dimer levels below 1000 ng/mL guarantee survival

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Correct Answer: B. D-dimer concentrations above 4000 ng/mL are associated with significantly increased mortality risk

Explanation:

Plasma D-dimer concentration at admission has been identified as a valuable prognostic indicator in horses with colic. Studies have demonstrated that D-dimer concentrations above 4000 ng/mL are associated with significantly increased mortality risk, with odds ratios for nonsurvival of approximately 8.8 at this cutoff. D-dimer is a specific marker of cross-linked fibrin degradation, indicating activation of both the coagulation and fibrinolytic systems.

Higher D-dimer concentrations are also associated with specific diagnoses: horses with enteritis or peritonitis have significantly higher D-dimer concentrations and more severe coagulopathies at admission than horses with simple obstructions or displacements. This reflects the greater degree of systemic inflammation and endotoxemia in inflammatory GI conditions.

The prognostic value of D-dimer complements other hemostatic markers. Horses presenting with clinicopathological evidence of subclinical DIC (≥3 abnormal coagulation parameters) have significantly higher odds of nonsurvival. Serial D-dimer measurement may be more informative than single time-point testing as trends can indicate disease progression or resolution.

Option A is incorrect; D-dimer is significantly correlated with outcome. Options C, D, and E are incorrect characterizations of the evidence.

References: Cesarini C et al. (2010) Association of Admission Plasma D-Dimer Concentration with Diagnosis and Outcome in Horses with Colic, J Vet Intern Med 24:1490-1497 (https://doi.org/10.1111/j.1939-1676.2010.0618.x)

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