Effect of sample collection material on detection of PRRSV antibody in oral fluid

Effect of sample collection material on detection of PRRSV antibody in oral fluid

C Olsen1, J Coetzee1, L Karriker1, A Kittawornrat1, S Lizano3, R Main1, A Meiszberg1, Y Panyasing1, C Wang1,2, J Zimmerman1

1Department of Veterinary Diagnostic and Production Animal Medicine, 2Department of Statistics, Iowa State University, Ames, IA, 3IDEXX Laboratories Inc., Westbrook, ME, cwolsen@iastate.edu

Introduction

The use of oral fluid in veterinary research and diagnostics has been the focus of recent investigations (2,3,4). The emphasis of the majority of this work has been on the detection of pathogen-specific antibody or PCR-detectable nucleic acid in samples collected using cotton rope. Reports in human diagnostic medicine suggested the material used to collect oral fluid samples quantitatively affected the detection of common assay targets, including hormones and antibody (1,5). Therefore, the objective of the present study was to determine if the material used to collect swine oral fluid affected the PRRSV oral fluid antibody ELISA response.

Materials and Methods

Oral fluid and serum samples were collected from two commercial wean-to-finish swine farms.

Serum was collected from five pigs in each pen and tested to establish pen PRRSV antibody status (IDEXX Laboratories, Inc., Westbrook, ME, USA).

Oral fluid samples (n = 3) were collected (2,3,4) using rope made of one of three collection materials: cotton (C), hemp (H) and nylon (N). To account for the possible effect of collection order on the detection of anti-PRRS antibody, samples were collected from pens in one of three sampling sequences: C-N-H, N-H-C, or H-C-N. Thereafter, oral fluid was assayed for PRRSV antibody using a commercial ELISA, as previously described.3

The effect of sampling material and collection order on the ELISA sample-to-positive (S/P) ratio were analyzed using a mixed effect two-way ANOVA model followed by Tukey-Kramer adjusted t-test (SAS® Enterprise Guide 4.3, Cary, NC, USA).

Results

Mean PRRSV ELISA S/P ratios are shown in Table 1. The two main effects (collection material, sampling order) had a statistically significant effect on the PRRSV ELISA S/P response. The interaction between material and order was not statistically significant (p = 0.52).

Conclusions and Discussion

Oral fluid specimens collected with cotton or hemp showed statistically higher mean antibody ELISA S/P values vs. samples collected with nylon rope. These data support the use of either hemp or cotton rope to collect oral fluid samples, but cotton rope is easier to handle and more highly absorbent (holds more fluid).

Table 1. Mean PRRS oral fluid ELISA S/P results on oral fluids collected from 104 pens

COLLECTION ORDER1

MATERIAL 1 2 3

Cotton 1.55 1.82 1.26 1.55a

Hemp 1.83 1.46 1.18 1.48a

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