Do you have QF 5.7 or 5.7-1? How old is your QF? What is the batch number? What caused your friend to fail? I recently tested some 5.7-1 from about 2 years ago with UrineCheck 7 validity strips. It passed, but was pretty marginal as far as creatinine compared to a sample of real urine. Try to get some more facts to share and maybe alleviate some concerns.