Which tests should be performed in the diagnosis of urethritis in males?

Updated: Jan 02, 2020
  • Author: John L Brusch, MD, FACP; Chief Editor: Michael Stuart Bronze, MD  more...
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In younger men, differentiation of UTI from urethritis may necessitate a urethral smear and culture or urinary antigen testing for chlamydia and N gonorrhoeae.

For urethritis, a urethral swab obtained 1 hour after the last micturition is 95% sensitive and 99% specific for gonorrhea. Inflammatory cells without intracellular gram-negative diplococci suggest nongonococcal urethritis (NGU).

A small swab should be carefully inserted approximately 1 inch into the male urethra and rotated about its axis 5 times. The swab then should be withdrawn and immediately streaked onto either chocolate agar or Thayer-Martin/New York City media. The same swab then should be rolled onto a slide, which should then be heat-fixed and stained (ie, Gram stain). Importantly, roll the specimen on only a very limited part of the slide; this will make the microscopic search easier. The same swab then may be sent for chlamydia testing, although many public health facilities do not have the funds to test males for this disease.

Chocolate agar is heated blood agar; the heating causes the red blood cells (RBCs) to lyse, releasing their intracellular contents, thereby enhancing the recovery of fastidious organisms such as N gonorrhea. This media is perfectly suited for culturing the male urethra, which is normally sterile. Thayer-Martin and New York City agars have antibiotics (including vancomycin) incorporated into them, thereby limiting the growth of competing bacteria that may overgrow the gonococcus.

These media are perfect for culturing the female cervix, the pharynx, or the anus. They also can be used for the male urethra, although the vancomycin may actually inhibit the growth of the gonococcus, creating a false-negative culture result. All neisserial growths must be confirmed as gonorrhea with a quadFERM test (a 2h carbohydrate degradation method for detecting Neisseria species); gonorrhea will only change the color in the glucose well.

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