Vaginal discharge — structured SAQ (15 marks)

(a) Diagnosis and Amsel criteria (4 marks)

One mark for the diagnosis; three for the criteria and threshold. ^[1][3]

• Diagnosis: bacterial vaginosis.
• The Amsel clinical criteria (CDC 2021 verbatim) require at least three of the following four: (1) homogeneous, thin discharge (milklike consistency) that smoothly coats the vaginal walls; (2) clue cells (vaginal epithelial cells studded with adherent bacteria) on microscopy; (3) vaginal fluid pH over 4.5; (4) a fishy odour before or after addition of 10% KOH (the whiff test).
• This woman has all four; three is the diagnostic threshold.^[1][3]

(b) Reference-standard laboratory method (3 marks)

One mark per point. ^[2][3]

• The Nugent score (a 0 to 10 Gram-stain score) is the reference-standard laboratory method.
• It weights three morphotypes: large gram-positive rods (Lactobacillus), small gram-variable/negative rods (Gardnerella/Bacteroides), and curved gram-variable rods (Mobiluncus).
• Interpretation: 0 to 3 normal (Lactobacillus-predominant), 4 to 6 intermediate, 7 to 10 bacterial vaginosis.^[2][3]

(c) CDC 2021 recommended regimens and counselling (5 marks)

One mark per option (max 3), one for the alternative-context, one for counselling. ^[3]

• Metronidazole 500 mg orally twice daily for 7 days, OR
• Metronidazole gel 0.75% one full applicator (5 g) intravaginally once daily for 5 days, OR
• Clindamycin cream 2% one full applicator (5 g) intravaginally at bedtime for 7 days.
• (Alternatives include secnidazole 2 g oral granules as a single dose and tinidazole regimens.)
• Counselling point: clindamycin cream is oil-based and weakens latex condoms and diaphragms for 5 days after use; advise an alternative contraceptive method during this window. (Also acceptable: routine treatment of male sex partners does not prevent recurrence; refraining from douching.)^[3]

(d) pH and inflammation contrast (3 marks)

One mark per condition correctly characterised. ^[1][3][4]

• Bacterial vaginosis — pH over 4.5, no inflammation (anaerobic dysbiosis, clue cells, fishy odour).
• Vulvovaginal candidiasis — normal pH (under 4.5), inflammation present (pruritus, erythema, curdy discharge; budding yeast/pseudohyphae on KOH prep).
• Aerobic vaginitis — pH often over 4.5, marked inflammation (yellow/purulent discharge, parabasal cells, abundant leucocytes; driven by aerobic organisms, distinct from BV and not treated with metronidazole).^[1][3][4]