Question: The ob-gyn performed a Nitrazine smear to check to see if a patient's amniotic fluid is leaking. How should I report this? Oregon Subscriber Answer: The code is 83986 (pH, body fluid, except blood). Some payers may also require modifier QW (CLIA waved test). To use this modifier, your physician must have a certificate of waiver under the Clinical Laboratory Improvement Amendments (CLIA). Nitrizine measures the pH of vaginal fluid. If the paper turns blue, amniotic fluid is present.