Motile trichomonads are seen on wet preparation in only 50% to 80% of culture-positive cases (SOR: B).50,54,56 Polymorphonuclear leukocytes can be dominant on wet mount, making visualization of trichomonads more difficult. The pH of the vaginal fluid is usually basic.
Trichomonas reported with cervical cytology
Trichomonas may also be reported on Pap smears. A meta-analysis57 comparing the pooled sensitivities and specificities of wet mounts and cytology demonstrated low sensitivities of 68% and 58%, respectively, and high specificities, 99.9% and 97%, respectively (SOR: A).
However, since cytology carries a 3% false-positive rate, its results are not diagnostic of trichomoniasis in low-risk, asymptomatic women.50,57 Treatment may be prescribed empirically based on positive cytology results. However, if an asymptomatic woman were concerned about whether she really has an STD, a positive wet prep would confirm the diagnosis. A negative wet prep should be followed up with culture to reliably rule out disease (SOR: B).
Trichomoniasis in pregnancy
Screening for asymptomatic trichomoniasis in pregnancy has not been recommended. In fact, some evidence suggests that treatment of trichomoniasis in pregnancy is associated with poorer pregnancy outcomes including lower birth weight and more prematurity (SOR: B).58,59
Aerobic vaginitis
Aerobic vaginitis is a term proposed to describe purulent vaginal discharge with predominance of abnormal aerobic flora.60 Aerobic vaginitis, which may be severe, has been reported as the cause of 5% of cases in a series from a specialty vaginitis clinic.61 The usual predominant microorganisms are group B streptococci, Escherichia coli, and Staphylococcus aureus. It is likely that less severe cases of aerobic vaginitis are not recognized in the primary care setting and are treated as BV or resolve spontaneously (SOR: C). The case series referred to above also reported good therapeutic response to 2% topical clindamycin (SOR: C).61
Noninfectious Vaginitis
Noninfectious causes of vaginal discharge include physiologic, irritant and allergic, cytolytic vaginitis, desquamative inflammatory vaginitis, collagen vascular disease, and idiopathic vaginitis.
Irritant and allergic vaginitis may result from sensitivities to topical medications, the active or base ingredients of spermicidal products, douching solutions, and the latex of condoms or diaphragms. If a woman with persistent symptoms has been using such intravaginal products, she should stop (SOR: C).
Cytolytic vaginitis is characterized by overgrowth of lactobacilli and cytolysis of squamous cells, including presence of cytoplasmic fragments and intact cells with naked nuclei.62 The cause is uncertain but may include a reaction to intravaginal medications or other products such as tampons. It can be found in up to 5% of women with symptoms and signs of vaginitis.62,63 Symptoms often mimic VVC and may include a white, cheesy discharge. Vaginal pH ranges from 3.5 to 5.5. Recurrences during luteal phase of the menstrual cycle have been described.64 Intravaginal antifungals should be discontinued. Baking soda sitz baths or douches are often used, but clinical trial data to support this practice are lacking (SOR: C).
Noninfectious desquamative inflammatory vaginitis (DIV) has also been described.65 DIV is an uncommon vaginitis characterized by profuse purulent discharge with epithelial cell exfoliation. It may occur at any time during the reproductive years or after menopause. There is probably a heterogeneous group of causes of DIV. Some cases may correspond to a disorder within the spectrum of lichen planus.66 Treatment is usually difficult, though there may be some response to local or systemic corticosteroid therapy (SOR: C).65
Differential diagnosis
A comparison of physical examination findings an diagnostic test results for various etiologies of vaginitis is summarized in Table 3 . An algorithmic approach to the differential diagnosis of abnormal vaginal discharge is presented in the Figure . Diagnosis is complicated in that signs and symptoms do little to help differentiate among BV, VVC, and trichomoniasis. A study2 of 22 genitourinary symptoms and signs showed that none differentiated among the 3 infections. This lack of clear-cut differences in symptoms also makes self-diagnosis and telephone triage inaccurate.67,68
A DNA probe testing system (Affirm VP III Microbial ID Test) for differential diagnosis is available but expensive. It identifies Gardnerella, Trichomonas, and Candida albicans with a sensitivity of 90% to 95%.54,66 The analyzer costs approximately $10,000 and would typically be purchased by a laboratory. Individual test kits cost about $27.
TABLE 3
Comparative findings among causes of vaginitis
| Cause | Physical exam findings* | Gold standard test | pH | Leukocytes | Wet mount | Alternative test |
|---|---|---|---|---|---|---|
| Bacterial vaginosis | Variable | Gram stain | >4.5 | No | Clue cells | Amsel’s criteria |
| Aerobic vaginitis | Abundant purulent discharge | Culture | >4.5 | Yes | Cocci or coarse rods | |
| Candida vaginitis | Adherent white disch. (thrush) | Culture | 3.8–4.5 | ± | Pseudohyphae or budding yeast | DNA testing |
| Non-Candida yeast vaginitis | Variable | Culture | Any | ± | Usually negative | |
| Trichomoniasis | Variable, occ. strawberry spots on cervix | Culture | >4.5 | ± | Motile trichomonads | DNA testing |
| Cytolytic vaginitis | Profuse discharge, often cheesy | Cytology and negative culture | 3.5–5.5 | ± | Overgrowth of lactobacilli and squamous cell fragments | |
| Desquamative inflammatory vaginitis | Abundant purulent discharge | Parabasal epithelial cells and negative culture | >4.5 | Yes | ||
| Irritant and allergic vaginitis | Variable, often erythema | None | Any | ± | ||
| * Helpful when present. | ||||||
FIGURE
Sequence of office tests to evaluate abnormal vaginal discharge
