Investigations
1st investigations to order
genital or lymph node specimens for nucleic acid amplification testing (NAAT)
Test
A presumptive diagnosis of LGV can be made with NAAT using urine and lymph node specimens as well as swabs of the urethra, rectum, cervix, and genital ulcers.[27] In the US, although NAAT is not cleared by the Food and Drug Administration for analysis of rectal or oropharyngeal specimens, the Centers for Disease Control and Prevention recommends NAAT testing for patients presenting with proctitis or extragenital infections.[27]
Result
positive for Chlamydia trachomatis (LGV and non-LGV genovars may be detected, but commercially available NAATs cannot distinguish between them)
swab via anoscopy for Gram staining
Test
Men who have sex with men who report receptive anal intercourse, particularly those who are HIV-positive, may warrant empirical treatment with this finding while awaiting other confirmatory tests.[21]
Result
anorectal Gram stain showing greater than 10 WBC/high-power field is suggestive of LGV
fluid or swab for LGV-specific molecular testing
Test
Definitive diagnosis can only be made with LGV-specific testing, such as PCR-based genotyping.
Specimens that are NAAT positive should be sent for confirmation by RT-PCR. Rectal swabs can be sent for PCR analysis.
Result
positive for LGV-specificC trachomatis genovars
STI testing
Investigations to consider
endoscopy with histopathology
Test
Those with signs and symptoms of proctocolitis may be referred for anoscopy or proctosigmoidoscopy. Colonoscopy may be considered if inflammatory bowel disease is suspected. Histologically, no pathognomonic features of LGV have been described, and findings with LGV may overlap with findings of inflammatory bowel disease, such as crypt abscesses and focal granuloma formation.[24][28]
Result
lesions in LGV are generally confined to the rectum and distal sigmoid colon, whereas Crohn's colitis can have a more varied colonic distribution; histopathology with LGV may reveal acute and chronic inflammation with less distortion of crypt architecture than is usually seen with inflammatory bowel disease
serum for complement fixation
Test
A complement fixation with a high titre in the absence of symptoms does not confirm LGV, and a low titre does not exclude LGV.
Result
a titre greater than 1:64 or a 4-fold rise between acute and convalescent specimens is suggestive of active LGV
serum for micro-immunofluorescence (MIF)
Test
Serotype-specific MIF has a higher sensitivity (>90%) and specificity than complement fixation, but similarly, it cannot distinguish past from present infection. MIF is not widely available.[34]
Result
a titre greater than 1:128 is strongly suggestive, but patients with LGV often have titres greater than 1:256
CT of abdomen and pelvis
Test
Imaging of the abdomen and pelvis is ordered when deep pelvic and rectosigmoid involvement is suspected.
Result
may indicate presence of strictures, deep pelvic lymph nodes
MRI of abdomen and pelvis
Test
Imaging of the abdomen and pelvis is ordered when deep pelvic and rectosigmoid involvement is suspected.
Result
may indicate presence of strictures, deep pelvic lymph nodes
fluid or swab for culture
Test
Isolation with tissue culture from fluid aspiration, genital, or rectal ulcers is the most specific study. Culture of C trachomatis has a yield of about 30%.[22] Techniques vary by laboratory, are not widely available as they are more demanding and less sensitive than other molecular techniques.
Result
positive for C trachomatis including LGV genovars
Emerging tests
fluid or swab for genovar typing
Test
For use with reference testing for epidemiological purposes.
Result
DNA sequencing of the major outer-membrane protein gene
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