Statistical note: With a 4-6% false positive rate, this device is only useful where there is a very high probability of infection. In much of the developed world where HIV infection rates are a fraction of one percent, this would mean that the overwhelming majority of positive tests are false positives.
the article claims a 0% false negative rate. This is a MUCH more important claim. False positives are fine, if scary, you go and get a proper test the next day.
