**2.4 Who are the candidates to test for chlamydial infections**

#### *2.4.1 Symptomatic and at-risk asymptomatic patients*

The diagnosis of *C. trachomatis* should be based on the clinical signs and symptoms associated with chlamydia in sexually active individuals. There is a high risk of infection and complications associated with chlamydia in sexually active patients. Most of these infections are asymptomatic because most chlamydial infections do not present any symptoms. Furthermore, chlamydia should also be tested on patients who have a history of documented gonococcal infection. Moreover, patients treated for chlamydia should be rescreened around 3 months after treatment, regardless of whether they think their sexual partners have been treated as well [44]. In the months following an initial infection with chlamydia, a high rate of reinfection has been documented as well [43, 48].

#### *2.4.2 Patients with persistent symptoms*

Symptoms that persist after appropriate treatment and good adherence to confirmed chlamydial infection are usually not the results of primary treatment failure. NAAT testing and ompA genotyping were used to characterize the reinfection or persisting infection rates in a longitudinal cohort of adolescent females assessed every 3 months [49]. There were 478 infections observed among 210 participants. Of these females, 121 experienced repeated infections. Only 2.2% were infections that persisted without documented treatment. Most of these infections (84%) were likely reinfections, 14% were probable or possible treatment failures, and 14% persisted without documented treatment.

#### *2.4.3 Recurrence of symptoms*

When chlamydia, gonorrhea, bacterial vaginosis, and other sexually transmitted diseases that cause urethritis or cervicitis have resolved after a first evaluation, a repeat evaluation is recommended for the prior treatment; NAAT remains the test of choice to diagnose reinfection in symptom recurrence [37]. Repeat diagnosis of chlamydia in previously treated patients usually indicates reinfection, as noted above [37].

Diagnosing *C. trachomatis* should also prompt testing for *N. gonorrhoeae* since both pathogens cause similar clinical syndromes and coexist in a significant proportion of patients with chlamydial infection [36].
