Genital or anal ulcer (herpes, syphilis, mpox, lymphogranuloma venereum, chancroid)

• Any acute genital ulcer is presumed to be syphilis: presumptive treatment can be given the same day, without waiting for results.

Swab of the base of the lesion (before any local treatment)

• Herpes simplex PCR (HSV-1 and HSV-2) with typing
• Treponema pallidum PCR on the lesion (not in the French laboratory fee schedule)if neededSuggestive chancre, especially during the window when serology is still negative, or oral or anal lesion: PCR is the preferred direct detection method ^[2]. Not listed in the NABM: specialised laboratory.
• Mpox PCR on the lesionif neededDiagnostic doubt (atypical appearance, undefined context of infection) ^[3,4]; sample by swabbing several lesions, mucous membranes preferably ^[3,5].
• Chlamydia trachomatis and gonococcus NAAT (PCR) on the lesion (or first-catch urine), with L genotyping if positiveif neededSuspected lymphogranuloma venereum: large inflammatory inguinal lymph node, anorectitis, man who has sex with men ^[6,7]. State “L genotyping requested”: it is done at the clinician’s request on a positive PCR ^[6].
• Haemophilus ducreyi PCR (chancroid, not in the French laboratory fee schedule)if neededContact in an endemic area (Africa, South-East Asia, South America) ^[8]: nucleic acid amplification can demonstrate the bacterium ^[9].

Laboratory tests

• Syphilis serology (treponemal test, then titrated non-treponemal test by the laboratory)
• HIV serology
• Hepatitis B serologyif neededTest for all other STIs ^[8]; the HAS specified this for mpox (HIV, HBV, HCV, syphilis, Chlamydia and gonococcus) ^[4].
• Hepatitis C serologyif neededTest for all other STIs ^[8]; the HAS specified this for mpox (HIV, HBV, HCV, syphilis, Chlamydia and gonococcus) ^[4].
• Chlamydia and gonococcus NAAT (PCR) on first-catch urine or self-collected sample (screening for associated STIs)if neededIf not already done on the lesion: all other STIs are to be tested for ^[8,10].

Repeat if the initial syphilis serology is negative

• Repeat syphilis serologyif needednon-French guidelineRecent chancre: treponemal test and non-treponemal test are negative before the chancre and during its first 5 to 15 days ^[2]. See the page “Positive syphilis serology”.

Swab of the lesion

• Herpes simplex PCR (HSV-1 and HSV-2) with typing

Laboratory tests

• HIV serology
• Syphilis serology (if not done for this episode)if neededThe American CDC (2021) includes it in the assessment of any genital, anal or perianal ulceration ^[11], and so does the Australian ASHM ^[14]. The SFD (French Society of Dermatology) asks for all other STIs to be tested for without naming it in the work-up of a chronic ulceration ^[8].
• FBC
• Type-specific herpes serology (HSV-1, HSV-2) if PCR is negativeif neededRecurrent or atypical lesions with negative PCR: anti-HSV-2 antibodies support the diagnosis of genital herpes ^[8,10].
• Biopsy of the lesion (with immunofluorescence if bullous dermatosis suspected): to be planned, not a laboratory test.