What ICD‑10 code should be assigned to a patient recently treated for chlamydia who is now asymptomatic and undergoing a test of cure?

ICD-10 Coding for Test of Cure After Chlamydia Treatment

For an asymptomatic patient recently treated for chlamydia who is now undergoing test of cure, use ICD-10 code A74.9 (Chlamydial infection, unspecified) or the site-specific code for the original infection location.

Rationale for Code Selection

The clinical guidelines explicitly state that test-of-cure is not routinely recommended for patients treated with standard regimens (doxycycline or azithromycin) unless therapeutic compliance is questioned, symptoms persist, or reinfection is suspected 1, 2. However, when test-of-cure is performed (particularly in pregnant women or after erythromycin treatment), the encounter still represents follow-up for a chlamydial infection.

Key Coding Considerations:

• The patient still has a history of recent chlamydia - The infection was recently diagnosed and treated, making the chlamydia diagnosis code appropriate for this follow-up encounter

• "Asymptomatic" does not mean "no diagnosis" - The absence of symptoms doesn't negate the need to code for the condition being evaluated. The test of cure is specifically checking for persistent chlamydial infection

• Administrative data accuracy - Research demonstrates that disease-specific ICD-10-CM codes (like A74.9 for chlamydia) have high positive predictive values (87.6%) and specificity (99.9%) for identifying persons with chlamydia 3

Appropriate ICD-10 Codes:

Primary options:

• A74.9 - Chlamydial infection, unspecified (most commonly used)
• A56.xx - Other sexually transmitted chlamydial diseases (site-specific codes based on original infection site)
  • A56.01 - Chlamydial cystitis and urethritis
  • A56.02 - Chlamydial vulvovaginitis
  • A56.19 - Other chlamydial infection of lower genitourinary tract

Common Pitfalls to Avoid:

1. Do not use Z codes for screening - This is not a screening encounter; it's follow-up for a known infection. Codes like Z11.3 (encounter for screening for infections with a predominantly sexual mode of transmission) would be inappropriate

2. Avoid "history of" codes - Do not use Z87.891 (personal history of sexually transmitted disease) as the primary code, since you're actively evaluating for persistent infection, not just documenting past history

3. Don't code as "contact with/exposure to" - Z20.2 (contact with and exposure to infections with a predominantly sexual mode of transmission) is incorrect for test of cure

4. Timing matters for coding accuracy - The diagnosis code should reflect that this is follow-up for a recently treated infection, not a new infection. Documentation should clearly indicate "test of cure" or "post-treatment evaluation"

Clinical Context from Guidelines:

The guidelines emphasize that test-of-cure should ideally be performed ≥3 weeks after treatment completion to avoid false-positive results from dead organisms or false-negative results from small numbers of organisms 1, 2. This timing consideration doesn't change the coding but should be documented clinically.

Important distinction: Rescreening at 3 months (recommended for women due to high reinfection rates) is different from test-of-cure and would potentially use the same chlamydia diagnosis code if positive, or could be coded as screening (Z11.3) if the patient is asymptomatic and the test is negative 2.