A comparison of two <i>M-hyo</i> ELISA test kits

By Noel Kavanah, thePigSite.com consultant - In this short article Noel Kavanah looks at the detection of antibodies to Mycoplasma hyopneumonia. The report evaluates two commercially available ELISA test kits and highlights the importance of validating test kits before using them under commercial conditions.
calendar icon 2 May 2001
clock icon 3 minute read

Background

Enzootic Pneumonia or Mycoplasmal Pneumonia of swine, a chronic disease with a high morbidity and a low mortality is caused by Mycoplasma hyopneumonia. The clinical signs include a chronic non-productive cough, retarded growth, slow onset and spread, and repeated occurrence of the disease.

A specific and sensitive serological test for the detection of antibodies to Mycoplasma hyopneumonia in porcine serum is required for the surveillance and precise diagnosis of the disease. The traditional methods for laboratory diagnosis of enzootic pneumonia by serology are complement fixation assay, indirect hemaglutination assay, and more recently ELISA.

Two commercially available tests were evaluated, the Dako Mycoplasma hyopneumonia ELISA test kit and a competitors Mycoplasma hyopneumonia ELISA test kit (Kit B).

Study

This study compared the results of the Dako ELISA (Kit A) with a commercially available kit (Kit B). Serum from 101 pigs from 17 different herds was used for this study. All herds were identified as being free from Mycoplasma hyopneumonia based on regular clinical veterinary inspection, slaughterhouse monitoring and serological monitoring.

Results

After testing with the Dako test kit, 100% of samples gave a negative to Mycoplasma hyopneumonia, so the ELISA test results correlated with the known Mycoplasma hyopneumonia status of the herds. When the same samples were tested by ELISA test kit B, only 70% of samples gave a negative result, 25% positive and 5% inconclusive.

Furthermore, on a herd basis, a false positive result was recorded in 13 out of 17 of the herds by Kit B.

Table 2. Results of DAKO and KIT B ELISA
antibody tests for Mycoplasma hyopneumonia on a herd basis.


Clinical
(Slaughter House)
DAKO ELISA KIT B ELISA
Number
%
Number
%
Number
%
No. Herds Tested
17
17
17
Positive
0
0
0
0
13
76.5
Inconclusive
0
0
0
0
1
6
Negative
17
100
17
100
3
17.5

Conclusions

False positives (and inconclusives) were identified when samples were tested using the test kit B, but not when the Dako test kit was used.

This highlights the importance of validating test kits before using them under commercial conditions. Also, especially in the case of Mycoplasma hyopneumonia infection, a declaration of herd Mycoplasma hyopneumonia status should be based on the results of a combination of clinical investigations, post-mortem examination, slaughterhouse checks of lungs and serology rather than one test only.
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