Reading P-TEST™ Results 

Q:

I have a 15 y.o. maiden, covered 4 times before having an embryo. Currently gestating at 7 months, the belly has grown. She's not stressed, not placentitus, with no cystic ovarian disease. I cannot read the test after 10 minutes. Can you tell me what you think?

 

A: Assess the color at both 1 minutes and 10 minutes.  If it was green to blue at 1 minute, then that is a positive.  The color at 10 minutes is an estimation of term. When you see a blue ring at the top, interpretation depends upon the sequence of color change. If it cleared from the bottom, likely the reagents did not get completely mixed at the start.   In that case, you can assume the test is valid and the bluish color is the correct answer. If the sample cleared completely and then the blue ring appeared, you need to ignore the blue and the amber color is the correct answer.  This can happen if an excess of air is introduced at the start.

Q:

I recently used P-TEST ™ Equine on my mare and the test came back pregnant - early term. What are the chances that a false positive show up as early term pregnant? My mare was scanned with ultrasound twice at 16 days and at 63 days by my vet. They didn’t find anything and said she was not pregnant. To me she looks like she has changed shapes and mood so I tested her with your test just as a sanity check. Would how well she has been drinking impact the overall color of the test?

 

A:

There are many reasons you can get a false positive.

  1. True false pregnancy or pseudopregnancy. Since your vet ultra-sounded the mare, she would have diagnosed that problem. You would see a dark blue color in that case. 

  2. Estrus. Horses are seasonal polyestrous breeders and only cycle when the day is lengthening. While it is not likely, she could be coming out of her anestrous season and has started to cycle.  To check that, you would need to retest in 10 days.  If the second test is negative, then she is not pregnant. If it's positive, then she is pregnant.

  3. Cystic ovary.  Here, the ovary contains a persistent follicle which pumps out estrogen and shows up as false positive - again usually dark blue. This condition will resolve itself with time, but the only way to eliminate this as the cause of the false positive is to palpate the ovary or to administer cystorelin which you absolutely do not want to do if you suspect she is pregnant. 

The two tests are nearly identical, but I see the second a little lighter green.    The hormone level has declined a bit.   For certain, this is not due to cycling.    It could just be due to natural variation between samples, but more than likely she is  {1}. pregnant or {2}.  anestrous with a cystic ovary.  This slight decline in hormone over time is exactly what you would see as the follicle resolves itself. I recommend to watch mare very closely for any signs of heat over the next days and retest in 10 days.

Q:

It was a bit harder to read P-TEST Strips as our goats are in the earlier stage of pregnancy. Do you happen to have a photo of what a negative test looks like? Does that little blue strip go completely yellow/amber if it's negative?

 

A:

You are right, it is more difficult to see the difference between a non-pregnant result vs early pregnancy. On the right, both strips are comparisons of a negative and a positive test. The wet paper does not appear yellow, but more of light gray color. So, it is difficult to differentiate light gray form light blue.  It helps a lot to hold the strip in front of a plain white background and use a bright light to illuminate the strip.