Grad Student Competition
Comparing 0.9% sterile saline to phosphate buffered saline as a transport media for Tritrichomonas foetus RT-qPCR testing
| Date/Time: |
9/13/2024
10:45
|
| Author: |
Tyler Jumper |
| Clinic: |
Mississippi State University |
| City, State, ZIP: |
Starkville, MS 39759 |
T.M. Jumper, DVM
1
;
M. Thoresen, PhD
1
;
E.H King, DVM, MS, DACT
1
;
D. Loy, DVM, PhD, DACVM
2
;
D. Loy, DVM, PhD, DACVM
2
;
D.R. Smith, DVM, PhD, DACVPM (Epidemiology)
1
;
1Department of Pathobiology and Population Medicine, College of Veterinary Medicine, Mississippi State University 240 Wise Center Drive Starkville, MS 39759
2Nebraska Veterinary Diagnostic Center, School of Veterinary and Biomedical Sciences, University of Nebraska-Lincoln 4040 East Campus Loop North Lincoln, NE 68583-0907
Introduction:
The limit of detection for T. foetus RT-qPCR is 1 organism/extraction in phosphate buffered saline (PBS) without prior culture. The objective of this study was to determine if 0.9% sterile saline (SAL), a readily available media, was not inferior to PBS as a transport media for T. foetus RT-qPCR testing at that concentration.
Materials and methods:
Smegma was collected via 10 weekly preputial washings from known T. foetus negative bulls. Each week, 1.3 mL of PBS with smegma (n=60) and 1.3 mL of SAL with smegma (n=60) were prepared. For each media, 30 samples were inoculated with T. foetus to a concentration of 1 organism/100 μL to evaluate sensitivity (Sn), 30 were left uninoculated to evaluate specificity (Sp). A total of 1200 (SnPBS=300, SnSAL=300, SpPBS=300, SpSAL=300) samples were tested by RT-qPCR. Differences in Sn and Sp between SAL and PBS were tested in logistic regression models, with week as a random effect. The Farrington-Manning test for noninferiority was used to evaluate the difference between diagnostic parameters with ∆=2.5%.
Results:
For PBS, Sn =70.7% (95%CI: 65.2-75.8%), and Sp=99.7% (95%CI: 98.2-100%); for SAL, the Sn=73.3% (95%CI:68.0-78.3%), and the Sp=100% (95%CI: 98.8-100%). No statistical differences between SAL and PBS were detected for Sn or Sp. The SpSAL was not inferior to SpPBS (p=0.008), however, noninferiority of SnSAL to SnPBS was inconclusive (p=0.08).
Significance:
The Sn for samples with very low concentration of T. foetus in SAL was similar to, and Sp was as good as PBS, suggesting either would be acceptable as transport media.
