For a Chlamydia (CGP) test in males, should a first-pass or mid-stream urine sample be used?

First-Pass Urine Collection is Recommended for Chlamydia Testing in Males

For Chlamydia (CGP) testing in males, first-pass (first-catch) urine should be used rather than mid-stream urine to maximize detection of the infection. 1, 2

Rationale for First-Pass Urine Collection

• First-pass urine contains a higher concentration of Chlamydia trachomatis organisms compared to mid-stream samples:

  • First 4-5 ml of urine contains approximately six times higher C. trachomatis organism load than regular urine cup specimens (32,533 versus 5,271 plasmids/ml) 2
  • Higher organism concentration leads to improved test sensitivity

• The Centers for Disease Control and Prevention (CDC) recognizes that first-catch urine samples are acceptable specimens for nucleic acid amplification tests (NAATs), which are the current gold standard for chlamydia detection 1

Proper Collection Technique

For optimal results when collecting first-pass urine samples:

• Patient should not have urinated for at least 2 hours prior to specimen collection 1
• Only the initial portion of the urine stream should be collected (first 15-30 ml)
• Specialized collection devices like FirstBurst can further improve detection by capturing only the first 4-5 ml of urine 2

Diagnostic Performance

• First-pass urine testing using NAATs offers:
  • High sensitivity (84-92%) 1
  • High specificity (>97%) 1
  • Non-invasive collection compared to urethral swabbing 3, 4

Alternative Collection Methods

While first-pass urine is recommended, other collection methods include:

• Self-collected urinary meatal swabs, which may detect more infections than first-catch urine in some studies (35 vs 33 cases in one study) 5
• Urethral swabs, which are more invasive but traditionally used 3

Important Considerations

• Urine collection is non-invasive and non-traumatic compared to urethral swabbing, improving patient acceptance 3, 4
• In symptomatic males, first-catch urine culture for N. gonorrhoeae has shown excellent sensitivity (100%) compared to urethral swabs 6
• For legal cases or sexual abuse investigations, culture methods using urethral swabs may still be preferred due to their near-100% specificity 7

First-pass urine collection represents the optimal balance of detection sensitivity and patient comfort for routine chlamydia testing in males.