Click HERE to download and view our PowerPoint presentation, with instructions and tips for using our in-house ringworm tests!

When trying to identify a positive result on the RW2 Ringworm Test it is important to check daily for simultaneous growth of the organism and colour change of the agar(s). When ringworm metabolizes, it causes a pH change in the medium (which contain pH indicators bromothymol blue and phenol red). Therefore when a white, fluffy culture is accompanied by a simultaneous colour change of the agar you are more than likely looking at a positive result.

If you have one of either a colour change or growth but not both simultaneously this is not indicative of a positive.

If the growth you see has a dark colouration to it, you are probably looking at a species other than ringworm.

If you embed your sample on the medium and you see a colour change but not growth, there might be some left over soap or disinfectant of some kind on the sample. If this occurs quickly, leave the sample to sit and see if the colour will revert back.

If your sample has sat longer than 10 days, you should be weary of anything that might grow from that day on. Positive results usually occur within 3-7 days and it’s usually on day 6 that you will start to see change.

If the agar begins to crack, you may have pushed the sample in too far. When embedding the sample, gently place it inside the agar and flip the plate upside down to prevent moisture contamination.

Additional Information (PDF)

The following are examples of negative and positive results with explanations:

This is a negative result. You can see a colour change, however the growth has a darker colouration not indicative of ringworm.

Courtesy of Oakville Humane

This is a negative result. As you can see, there is no discernible colour change, and the growth is almost mouldy.

Courtesy of KW Humane

This was an example of a test that we suggested the clinic redo. It was a case of the DTM changing colour with white fluffy growth, but the ESA didn’t change colour with the white fluffy growth. It looked positive, but we suggested they retest to confirm.

Courtesy of Oakville Humane

This was a negative result. The growth has a discernible discolouration and there is relatively no colour change. The slight colour change on the edge of the growth is most likely due to outside factors. As you will see in the next pictures the colour change will be very obvious for positives.

Courtesy of Veterinaire Des Chats

This is a clear positive. You can see the white, fluffy growth and the colour change is very obvious. The DTM turned red and the ESA turned blue.

Courtesy of Cumberland Vet




This is actually a positive from a guinea pig. The growth almost looks like a paint splatter, but nonetheless it is still white and fluffy and the colour change is extremely obvious. 

Courtesy of Glenview Animal Hospital





 PLEASE NOTE: Our RW2 plates now come in a round shape. The surface area is identical, however various improvements will be seen.

1) The new round format is much less susceptible to breakage during shipment. 

2) The actual petri-dish is deeper allowing for an increase in fill volume. This prevents the agar from drying out during the long incubation period. 

3) Breathing vents have been added to the new dish to allow for a better exchange of oxygen to the sample and decrease excess moisture during storage. 


 Please don't hesitate to contact Sensor Health with any questions!