Point of Care Testing: Vaginal pH

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Point of Care TestingVaginal pH

• Eberhard Fiebig, MD
• Director, SFGH Clinical Laboratory

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Purpose (Indications)
pH Testing is Helpful in the Diagnosis of

• ruptured amniotic membranes in pregnancy
• bacterial vaginosis and trichomonas infection

Ruptured Membranes
Bacterial Vaginosis
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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 gt4.5
• 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
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Sample

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

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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

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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
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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.

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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 Labs POCT
  services (206-8588).

Everyone should see 12
Persons with normal color vision should see 26
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References

• Simoes JA, Discacciati MG, Brolazo EM, Portugal
  PM, Dini DV, Dantas MCM. Clinical diagnosis of
  bacterial vaginosis. Intl J Gyncol Obstet
  20069428-32.
• Davidson, KM. Detection of premature rupture of
  the membranes. Clin Obstet Gyncol
  199134(4)715-722.

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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

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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

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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 patients chart.
• All of the above is correct.

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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

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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