July 26, 2017

The Evils of Expired Pregnancy Tests

I’m sure it’s no surprise to regular readers that I’m frugal to borderline cheap. Buying pregnancy tests in bulk, and saving the extras are well within my normal frugal tendencies. So when Domingo and I decided to start trying for a third child, I planned to use those left over pregnancy tests I had saved. We had succeeded in conceiving Alexis much sooner than I anticipated, so I had quite a few left over. The only problem? They had expired in April of 2015 and it was nearing the end of 2016.

I did some research online and the general consensus was that an expired pregnancy test was fine to use. The older the test, the more likely it had lost some sensitivity to hCG, the human pregnancy hormone. An expired test is therefore more likely to give a false negative reading. Since are few conditions where one would have hCG in their system and not be pregnant, a false positive is unlikely in general. Therefore, I concluded, the primary risk of using an expired test is that I might have to wait a little longer to find out the good news. If I was pregnant, hCG would slowly increase in my system and eventually be enough for the expired test to pick up. What’s a few extra days wait?

If only that was my experience. Instead I was treated to a new kind of false positive I had never heard of before, the disappearing false positive.

To back track a little, the main form of false positive is an evaporation (evap) line which happens when the test strip dries in such a way that the second line is visible. A tall tell sign of an evap line is the line is grey, and appears after the testing time window, when the test is dry. Generally speaking, a line within the testing window should be considered positive.

The second month we tried, the second line indicating a positive appeared at the 4 minute 30 second mark. It was a full thirty seconds within the time window. Hurray, pregnant!

I’m the kind of obsessive person who likes to go back and look at the positive test throughout the day, take pictures of it, etc. I do the same with negative tests too, minus the pictures of course. Two hours later I could only see the second line while holding the strip under a bright lamp and holding it at just the right angle. A little while later I couldn’t even see it then. I wondered if my eyes were playing tricks on me. I tried not to let my mind dwell on the second line that was no longer there. If I was pregnant, I rationalized, I’d get another positive test in the next day or two. I tested the next day, and the next, and the next. Negative across the board.

Two months later the same thing happened. This time the second line was more pronounced, and appeared at the two minute mark. It didn’t fade away into nothingness until 6 hours later. This time I was a little more mentally prepared for the possibility that I might not be pregnant.

After doing some digging online I found a line that disappeared within 24 hours is exceedingly rare, the result of a faulty test and should be considered as a negative. My frugal tendencies had lead to unnecessary heartache.

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