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Editor,—The advent of ligase chain reaction (LCR) and other DNA technologies and their greater sensitivity1 has allowed the possibility of taking samples other than from the urethra in men, including urine samples.2–5
Although urine samples have the advantage of being collected non-invasively, the sensitivity of LCR tests on such samples is less than for urethral samples.2 This may be due to the presence of inhibitors in urine.6 The reduced sensitivity on urine samples may be unacceptable, particularly if testing populations with a high prevalence of chlamydia infection. Furthermore processing of urine samples is more laborious.
It is currently recommended that specimens for the detection of genital Chlamydia trachomatis infection by LCR are taken 2–4 cm from the urethral orifice and the swab rotated for 3.5 seconds.7 Many men are unable to tolerate this. It is often painful and may discourage patients from seeking medical attention.
A pilot study was conducted to compare the sensitivity of LCR testing for genital chlamydial infection in men, taken from the meatus itself against the standard technique.
All male patients attending the GUM clinic over a 3 month period were included in the study if they had symptoms or signs compatible with chlamydia, or if a contact of a known case of chlamydia. A swab was taken from the urethra in the standard fashion. A second swab was taken from the meatus. After the sixth week of the study the order of the first and second swabs was changed, in order to evaluate any bias related to the order of the swabs. Specimens were processed using Abbott Laboratories LCx Chlamydia and handled according to the manufacturer's guidelines.
Twenty five patients were asked to evaluate the swabs and to state which swab caused least discomfort or if there was no difference between them. A total of 208 men were recruited to the study. The overall prevalence of genital chlamydia infection in our population was 25% (52/208). A confirmed diagnosis was made if both of the samples performed from the same man were positive for chlamydia, or if one sample was positive together with an equivocal result. There were no false positive tests using these criteria giving all methods a specificity of 100%.
There was no significant difference in detection rates between the subgroups where the order of swabs was changed.
There was no significant difference in the sensitivity of samples taken from the meatus (100%) or from deep within the urethra (96.2%). Of the 25 men questioned two (8%) felt that the meatal swab caused more discomfort; 19 (76%) had a strong preference for the meatal technique. Only four men (16%) stated the swabs were similar in terms of discomfort.
A meatal swab for the detection of chlamydia is more acceptable to patients and has a similar sensitivity to the traditional technique of urethral sampling
Urine samples, although non-invasive, are less likely to yield a positive diagnosis compared to urethral/meatal swabs and require extra processing by laboratories.
In a high prevalence setting (such as a sexual health clinic), the meatal technique provides a specific, highly sensitive, and well tolerated sampling method for the detection of chlamydia infection in men.
Further studies to confirm our findings in symptomatic, and asymptomatic, chlamydia infection are needed before introducing this technique as routine clinical practice.
Contributors: HL, principal investigator and author; SMM, investigator and edited final draft; JLD, data collection and obtained clinical specimens; MSS, investigator and processed specimens.