pH testing in the assessment of vaginal discharge

Last edited 05/2019 and last reviewed 03/2022

Point of care testing for pH of vaginal discharge

• the pH of vaginal discharge can be very helpful in making a diagnosis during examination
  
  
• most patients should have bedside pH testing of vaginal discharge in preference to taking a HVS
  
  
• vaginal secretions should be collected from the lateral vaginal walls using a swab or small loop. The sample should be applied to narrow range pH paper (pH 4-7)
  
  
• vaginal pH testing can be used to assess the likelihood of Candida (pH < 4.5) or of BV or TV (pH >4.5) but it cannot distinguish between BV and TV (1)
  • thus a bedside diagnosis can be made on the basis of history plus clinical signs and the pH of the discharge

   

A HVS is not recommended in routine cases as it is unlikely to be of significant diagnostic value (2):

• situations where an HVS is indicated are:
  • postnatal infection
  • pre & post termination of pregnancy
  • pre & post-operative gynaecological surgery
  • persistent or recurrent (>=4 episodes/year) symptoms
  • symptoms not characteristic of candida or BV

Reference:

• Sexually transmitted infections in primary care. RCGP Sex, Drugs, HIV and Viral Hepatitis Group and BASHH, 2013
• Jungmann E, Johnson AM, Ridgway G, Durrant K, Robinson AJ. How useful are high vaginal swabs in general practice? Results of a multicentre study.Int J STD AIDS 2004; 15: 238-129
• Oxfordshire Clinical Commissioning Group. Investigation and Management of Vaginal Discharge in Adult Women (Accessed 23/5/19)