Point of Care Testing: Vaginal pH

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

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

3. Principle pH Paper Strips… • Fluid from the upper vagina is normally acidic (pH 3.8-4.5) • Leakage of amniotic fluid (normal pH 7.0-7.5) 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

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

5. 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

6. 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

7. 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.

8. 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 (206-8588). Everyone should see “12” Persons with normal color vision should see “26”

9. References • Simoes JA, Discacciati MG, Brolazo EM, Portugal PM, Dini DV, Dantas MCM. Clinical diagnosis of bacterial vaginosis. Intl J Gyncol Obstet 2006;94:28-32. • Davidson, KM. Detection of premature rupture of the membranes. Clin Obstet Gyncol 1991;34(4):715-722.

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

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

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

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

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