• Etiologic diagnosis: identifying the organism causing symptoms with microscopy or laboratory tests. Such tests are expensive or time-consuming. For example, culturing techniques can accurately detect chancroid, chlamydia, and gonorrhea but cost US$12 to $40 and require one to six days to incubate specimens in a laboratory (229, 283). The widely used rapid tests for syphilis, the rapid plasma reagin (RPR) test and the Venereal Disease Research Laboratory (VDRL) test, require needles and syringes to obtain venous blood and a centrifuge to separate plasma from red blood cells (286).
• Clinical diagnosis: identifying the STD causing symptoms based on clinical experience. Even experienced STD service providers, however, often misdiagnose STDs when they rely only on their clinical experience (125). In a South African study of 100 men and 100 women with genital ulcers, for example, clinicians correctly identified only about one-third of the cases of chancroid or syphilis in the men, about one-half of cases in the women, and less than 10% of mixed infections (210).

• Syndromic diagnosis: identifying all possible STDs that could cause symptoms (see sidebar, The Syndromic Approach). Flow charts formalizing the syndromic approach, such as the wall chart published in this issue of Population Reports, give providers step-by-step instructions to diagnose STDs and list drugs recommended by WHO to treat them.

Treatment includes relieving discomfort. Patients in pain may avoid urinating or drinking water and thus risk getting urinary tract infections or becoming dehydrated. Providers can advise patients to clean a genital ulcer—for example, with salt water and, if possible, to soak in dilute salt water, which can help to clean and dry up an ulcer (19, 34).