What are the signs and symptoms of bacterial vaginosis (BV) vs trichomoniasis vs gonococcal infection vs chlamydia in a sexually active adult female with a history of sexually transmitted infections (STIs)?

Clinical Differentiation of Common Vaginal and Cervical Infections

The four conditions present with distinct discharge characteristics and symptom patterns that allow clinical differentiation: bacterial vaginosis produces thin gray-white discharge with fishy odor and minimal irritation; trichomoniasis causes profuse yellow-green frothy discharge with severe pruritus; while gonorrhea and chlamydia typically manifest as mucopurulent cervicitis with abnormal bleeding rather than classic vaginitis symptoms. 1

Bacterial Vaginosis (BV)

Clinical Presentation

• Thin, homogeneous white-to-gray discharge that adheres to vaginal walls 2, 1
• Distinctive fishy odor that intensifies after intercourse or with alkaline exposure (KOH "whiff test") 2, 1
• Minimal or absent pruritus and vulvar irritation—this is a key distinguishing feature from other infections 1
• Vaginal pH elevated above 4.5 1
• Approximately 50% of women meeting diagnostic criteria remain asymptomatic 2, 1

Diagnostic Findings

• Clue cells on wet mount microscopy 2
• Positive whiff test with 10% KOH 2
• Gram stain showing predominance of anaerobic bacteria with sensitivity of 90% 2

Important Caveat

Standard clinical testing can miss 20-30% of BV cases, making it the most commonly missed diagnosis in women with malodorous discharge 2. If initial testing is negative but symptoms persist, retesting with Gram stain or DNA probe is recommended 2.

Trichomoniasis

Clinical Presentation

• Profuse, yellow-green, frothy discharge with characteristic appearance 1, 3
• Malodorous or musty odor (different quality than BV's fishy smell) 1
• Moderate to severe vulvar irritation and pruritus—a distinguishing feature from BV 1
• Vaginal pH elevated above 4.5 1
• "Moth-eaten" or strawberry cervix appearance in only 13% of cases but highly specific when present 4
• Approximately 70% of infections are asymptomatic 3

Diagnostic Findings

• Motile trichomonads on wet mount (sensitivity only 60-70%) 5
• Nucleic acid amplification tests (NAATs) with sensitivity 86.1-100% 3
• Parabasal cells present in 73% of cases 4

Key Distinction from BV

While both conditions share elevated pH and can have malodor, trichomoniasis causes significant vulvar symptoms and inflammation, whereas BV does not 1, 4. Clue cells are generally absent in pure trichomoniasis but when present indicate concomitant BV 6.

Gonococcal Infection

Clinical Presentation

• Mucopurulent cervicitis (MPC) with yellow endocervical exudate visible in the endocervical canal 1
• Abnormal vaginal bleeding (intermenstrual or postcoital) is more characteristic than discharge 5, 1
• Pruritus is NOT a prominent feature—this distinguishes it from trichomoniasis and candidiasis 1
• Vaginal discharge, when present, is secondary to cervical infection 5
• Majority of cervical infections are asymptomatic; 53-100% of extragenital infections are asymptomatic 3

Diagnostic Findings

• Culture or NAAT from endocervical specimens with sensitivity/specificity 97.1-100% 5, 3
• Testing should include urethral, rectal, and pharyngeal sites in at-risk populations 5

Critical Consideration

Chlamydial and gonococcal infections in females are of special concern because of the possibility of ascending infection leading to PID, ectopic pregnancy, and infertility 5.

Chlamydial Infection

Clinical Presentation

• Mucopurulent cervicitis similar to gonorrhea with yellow cervical discharge 5, 1
• Abnormal vaginal bleeding more common than discharge complaints 5
• Minimal to absent pruritus—distinguishes from trichomoniasis 1
• Most infections are asymptomatic in both men and women 5
• Some women with apparently uncomplicated cervical infection already have subclinical upper reproductive tract infection 5

Diagnostic Findings

• NAATs from endocervical, vaginal, or urine specimens with sensitivity/specificity 97.1-100% 5, 3
• Culture less commonly available but can be used for test-of-cure 5

Important Clinical Point

Coinfection with chlamydia occurs frequently in patients with gonococcal infection, making presumptive dual treatment appropriate 5.

Diagnostic Algorithm Using pH and Microscopy

This rapid bedside approach provides accurate diagnosis in most cases: 1

1. Measure vaginal pH:

   • pH ≤4.5 suggests candidiasis or non-infectious causes 1
   • pH >4.5 suggests BV, trichomoniasis, or cervicitis 1

2. Perform wet mount microscopy:

   • Clue cells + fishy odor = BV 1
   • Motile trichomonads = trichomoniasis 1
   • Yeast/pseudohyphae + severe pruritus = candidiasis 1

3. Examine cervix:

   • Yellow mucopurulent discharge from os = test for gonorrhea/chlamydia 1

Overlapping Features and Pitfalls

Common Diagnostic Challenges

• BV and trichomoniasis share multiple features: elevated pH, malodor, homogeneous discharge, and overgrowth of anaerobic bacteria 6, 4
• Mixed infections occur frequently: trichomoniasis can interfere with Gram stain diagnosis of BV 6
• White discharge is non-specific: while classically associated with candidiasis, BV can also produce white or gray discharge 2
• Asymptomatic infections are the norm: 50% of BV, 70% of trichomoniasis, and majority of gonorrhea/chlamydia cases lack symptoms 2, 1, 3

Critical Distinguishing Features

The presence and severity of pruritus is the most useful clinical discriminator: 1

• Severe pruritus = candidiasis or trichomoniasis
• Moderate pruritus = trichomoniasis
• Minimal/absent pruritus = BV, gonorrhea, or chlamydia

The character of discharge provides secondary clues: 1

• Thin gray with fishy odor = BV
• Profuse yellow-green frothy = trichomoniasis
• Yellow cervical mucus = gonorrhea/chlamydia

Testing Recommendations

When clinical diagnosis is uncertain or symptoms persist despite treatment, NAAT testing for all four conditions should be performed, as these tests have superior sensitivity (86.1-100%) and specificity (97.1-100%) compared to microscopy 3. Testing for gonorrhea and chlamydia should always be performed together given high coinfection rates 5.