22% of all semen detections are PSA positive when the AP test is false negative. Three percent of all semen detections are PSA negative and AP false positive.  Select this link for specific statistics.

 

	All AP tests are presumptive (other chemicals can cause a positive reaction).  We do not recommend purchasing any AP home test.  If the outcome of a semen detection test could cause family or relationship termination you should consider purchasing our laboratory test which is not presumptive due to the PSA test or at a minimum, you should consider using the PSA home test kit.
	AP chemicals become less effective with time.  There is no time dating of many AP test kits sold on the internet.

 

While it is generally accepted that high concentrations of acid phosphatase are present in semen, it should be reiterated that a positive test for the enzyme is not conclusive evidence as to the identity of a stain as semen.  The enzyme occurs in other human tissues and biological fluids including vaginal secretions (also in other animals as well as plants).

Abstract from New England Journal of Medicine "Of 27 vaginal fluid samples from women who were allegedly raped in which the acid phosphatase test was negative, 7 (26 per cent) were unequivocally positive for p30¹  by our assay. We conclude that the assay for p30¹  offers a more sensitive and specific method of semen detection in rape investigation than the enzyme assay for prostatic acid phosphatase." ¹ - P30 is a Prostate Specific Antigen (PSA)

Panty samples can test positive for acid phosphatase (AP) with a negative semen detection outcome (PSA and microscopic) which then can be confirmed by the absence of a male DNA profile.  Here are recent test examples.

 

Acid Phosphatase (AP) cannot be detected in semen at concentrations less then 78 ng which has been confirmed by our internal validation study that is consistent with other validation studies and published data.

 

Misrepresentation of AP and PSA semen detections on the Internet.