Point of Care Testing: Vaginal pH Eberhard Fiebig, MD Director, SFGH Clinical Laboratory

Purpose (Indications) ruptured amniotic membranes in pregnancy bacterial vaginosis and trichomonas infection pH Testing is Helpful in the Diagnosis of: Ruptured MembranesBacterial Vaginosis

Principle Fluid from the upper vagina is normally acidic (pH ) Leakage of amniotic fluid (normal pH ) OR bacterial overgrowth raises the pH to >4.5 The pH paper is impregnated with the dye nitrazine (phenaphtazine) which changes color from yellow to blue as pH increases from 4.5 to ≥ 7.0 Changes in color shades occur in pH increments of 0.5, allowing semiquantitative pH measures when the color of the pH paper is compared to a standard color chart supplied with each roll of pH paper …at pH 4.0 and 7.0 pH Paper Strips…

Sample Pooled vaginal fluid sampled with a cotton swab during speculum examination

Testing Apply cotton tip soaked in vaginal fluid to pH paper Observe the paper for immediate color change by comparing to the color chart in the dispenser Record pH value corresponding to the color chart

Quality Control Quality control (QC) of pH paper is performed by the Clinical Laboratory on shipment samples before release. QC consists of verification of the appropriate color reaction against certified buffer solutions. Verified papers will be given an expiration date of 1 year from QC. The expiration date is printed on a label attached to each paper roll dispenser. pH Paper without expiration date label on the dispenser or pH paper past the expiration date MUST NOT BE USED. Expiration Date on Dispenser

Limitations False positive (elevated) pH values may occur due to alkalinization of the vagina by blood, semen, urine, soap, antiseptic solutions, antibiotic therapy and infections. False negative pH values (failure to detect elevated pH as a result from ruptured membranes) may occur due to decreased efflux of amniotic fluid as the time between membrane rupture and testing increases.

Are You Color Fit? Interpretation of vaginal pH test results may be affected by poor color vision. Up to 10% males and 0.4% females may be color deficient to some degree. If you have not done so already, have your color vision checked if you perform point of care tests or other tasks that require color discrimination. New employees are color tested as part of the orientation process. Existing employees should make an appointment with SFGH Clin Lab’s POCT services ( ). Everyone should see “12” Persons with normal color vision should see “26”

References Simoes JA, Discacciati MG, Brolazo EM, Portugal PM, Dini DV, Dantas MCM. Clinical diagnosis of bacterial vaginosis. Intl J Gyncol Obstet 2006;94: Davidson, KM. Detection of premature rupture of the membranes. Clin Obstet Gyncol 1991;34(4):

Vaginal pH Quiz 1. Vaginal pH Testing is Intended for: A.Exact pH measurement of vaginal fluid B.Aiding in the diagnosis of ruptured membranes in pregnancy, bacterial vaginosis and trichomonas infection C.Exclusion of pregnancy D.Diagnosis of herpes infection E.Screening for vaginal bleeding

Vaginal pH Quiz 2. Vaginal pH Measurement is based on: A.Color change of pH paper from yellow to red B.Color change of pH paper between pH 1.0 – 4.0 C.Change in color of pH paper from yellow to blue D.Random color changes as pH increases E.Change in color shade every 2 pH points

Vaginal pH Quiz 3. Vaginal pH Testing is performed by: A.Collection of vaginal fluid by cotton swab during speculum exam. B.Touching the pH paper with cotton tip containing collected vaginal fluid. C.Observing pH paper for immediate color change by comparing to standard color chart. D.Recording the pH value, corresponding to the color change in the patient’s chart. E.All of the above is correct.

Vaginal pH Quiz 4. Quality Control of the Vaginal pH Test A.Is performed by the Clinical Laboratory B.Consists of verifying the performance of a sample of pH paper against certified buffer solutions C.Is documented by the Clinical Laboratory through placing a label with an expiration date on individual pH paper dispensers D.Allows the pH paper to be used until the expiration date which is 1 year from when QC was performed E.All of the above is correct

Vaginal pH Quiz 5. Limitations of Vaginal pH Testing include A.pH paper does not work very well in the relevant range between pH 4.0 and 7.0 B.It takes a while for pH paper to change color after coming in touch with vaginal fluid C.pH paper is only useful for detecting ruptured membranes in pregnancy D.False elevation of vaginal pH may be caused by urine, blood, semen, soap and antiseptic solutions E.All of the above are correct