Literature review > Issue 9 > Review on Foo  et al. 

Non-gonococcal urethritis (NGU) is a frequent cause of urethral symptoms in men. The diagnosis of NGU is made by the absence of Gram negative intracellular diplococci on a urethral smear and the presence of 5 or more polymorphonuclear leucocytes (PMNs) per high power field (hpf) or the presence of 10 or more PMNs per hpf on a Gram stained preparation of a first pass urine specimen. Chlamydia trachomatis accounts for 30-50% of cases of NGU. Some studies have found that C. trachomatis is detected less often in men with a positive urethral smear who are asymptomatic than those who are symptomatic. In other studies, C. trachomatis is frequently detected in men with a positive urethral smear regardless of the presence or absence of urethral symptoms.

Foo et al. investigated the correlation of symptoms, signs, and urethral smear microscopy with the detection of C. trachomatis in men. A total of 111 men diagnosed with C. trachomatis in a genitourinary medicine clinic were analyzed retrospectively. Patients were considered symptomatic if they reported a discharge, dysuria, or penile irritation or had meatal inflammation or urethral discharge on examination. The diagnosis of NGU was based on the microscopic detection of more than 5 PMNs per hpf in a urethral smear and/or more than 10 PMNs per hpf in a first pass urine specimen. Chlamydia infection was detected by strand displacement amplification (SDA; Becton Dickinson, Sparks MD) performed on a urethral specimen. Of the 111 men with C. trachomatis infection, 70 (63%) were symptomatic and 41 (37%) were asymptomatic. Among the symptomatic men, 59 (84%) had NGU on microscopy and were treated for chlamydia during their initial clinic visit, including 7 who were contacts of chlamydia infection, and 11 (16%) did not have NGU, of whom 6 were treated based on symptoms alone and 5 were not treated initially. Among the asymptomatic men, 21 (51%) had NGU on microscopy and were treated during their initial clinic visit, including 11 who were contacts of chlamydia infection, and 20 (49%) did not have NGU, of whom 3 were treated because they were contacts of chlamydia infection or for other reasons and 17 were not treated initially. Thus, of the 111 men with C. trachomatis infection, 21 (19%) received treatment during their initial clinic visit solely on the basis of microscopy. The authors concluded that testing asymptomatic men attending genitourinary medicine clinics for NGU by microscopy is warranted.

Other recent studies have evaluated the relation between C. trachomatis infection in men and urethral smear microscopy. Haddow et al. [1] collected data from 363 men attending a genitourinary medicine clinic who had a urethral smear and a urethral ligase chain reaction (LCR; Abbott Laboratories, Abbott Park, IL) test for C. trachomatis. Of these men, 30 (8%) had C. trachomatis infection and 96 (26%) had NGU on microscopy. NGU was detected in 19 men with chlamydia and in 77 men without chlamydia. Thus, a positive urethral smear was only 63% sensitive and 77% specific for C. trachomatis infection and had a positive predictive value of only 20% and a negative predictive value of 96%. The authors concluded that younger age and the presence of urethral symptoms were as predictive as a positive urethral smear for chlamydial urethritis.

Iser et al. [2] recently conducted a case-control study of heterosexual men with non-gonococcal urethral symptoms and controls without urethral symptoms. Symptomatic cases had a urethral smear collected and examined for PMNs. All participants provided a first pass urine specimen that was tested for C. trachomatis by LCR as well as for other potential pathogens. Among the 80 cases with urethral symptoms, 49 (61%) had NGU on microscopy and 17 (21%) had C. trachomatis infection. C. trachomatis was detected in 12 (24%) of the cases with NGU and in 5 (16%) of the cases without NGU. Only 1 (1%) of 79 asymptomatic controls had C. trachomatis infection. The authors concluded that microscopy of the urethral smear does not help to identify which men with urethral symptoms should be treated for chlamydia.

Overall, these studies suggest that urethral smear microscopy has limited value for identifying men with chlamydial infection, although it may facilitate treatment of asymptomatic men during their initial clinic visit.

References:

1. Haddow LJ, Bunn A, Copas AJ, Gilson R, Prince M, Ridgway GL, Sadiq ST. Polymorph count for predicting non-gonococcal urethral infection: a model using Chlamydia trachomatis diagnosed by ligase chain reaction. Sex Trans Infect 2004; 80:198-200.

2. Iser P, Read TRH, Tabrizi S, Bradshaw C, Lee D, Howarth L, Garland S, Denham I, Fairley CK. Symptoms of non-gonococcal urethritis in heterosexual men: a case control study. Sex Transm Infect 2005; 81:163-165.

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