I've just been complaining to the manufacturers of some pregnancy tests in the 99p shop. A couple of years ago I got a faint positive on one, rushed out to buy a FRER, which was negative, and hence wasted £10. This weekend I didn't have any of my normal ones left, and at 13dpo bought another one and got a faint positive. The next day my period came. The box says over 90% accurate, which is of course quite rubbish as I pointed out to them.
However, they replied, saying they were actually 99% accurate, but at the time they manufactured that batch, they were only allowed to state 'over 90%' by law. These were the reasons they gave for my false positive.
'With regards to the false positive result experienced, there could be a number of factors which could produce this result;
1 The test has a sensitivity of 25MIU, so this could be due to the test being completed at the very early stages of pregnancy.
2 As the false positive was a faint line, this could simply be due to the natural monthly cycle.
3 Hormone drugs could also produce a false positive, including steroids, contraceptives or HRT medication.'
We all know that number 3 is rubbish, as is categorically stated in their own leaflet, and wtf does number 2 mean exactly? If our natural monthly cycles could produce a false positive, there would hardly be any point in making pregnancy tests!