Short answer

Different infections live in different places, so testing samples the right site with the right technology: NAAT on urine or swabs finds bacterial DNA (chlamydia, gonorrhea, trichomoniasis) at genital, throat, and rectal sites; blood tests find immune responses and viral markers (HIV, syphilis, hepatitis, herpes antibodies) with longer windows.

No single sample covers everything. Complete panels combine urine-or-swab NAAT with blood draws plus site-specific swabs in the same visit.

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Urine testing. Convenient, urethra-bound

First-catch urine (initial stream after a 1–2-hour hold) powers NAAT for chlamydia, gonorrhea, and trichomoniasis where assays include it. Accurate for urethral infection, rivaling swabs at that site.

Blind to throat infections, rectal infections, blood-borne infections, herpes (needs sore swabs), HPV effects, and cervical conditions.

Opposite of midstream UTI technique (which discards the first portion). Clinics specify when both run together.

Detail at Urine Tests for STIs: What They Detect.

Swab testing. Every exposed surface, sampled directly

  • Vaginal swabs (often self-collected. Painless, highly accurate, preferred in many settings).
  • Cervical swabs during speculum examinations.
  • Penile and urethral swabs (less common now. Urine largely replacing them).
  • Throat swabs after oral exposure (silent pharyngeal infections needing direct sampling).
  • Rectal swabs after anal exposure (self-collection validated. Private, instructed, equally accurate).
  • Sore swabs diagnosing herpes with typing (fresh beats healed).
  • Cervical samples doubling for Pap/HPV screening (different analysis, cytology and HPV DNA, not STI NAAT, collected in the same position).

Swab experience in full: Swab Tests for STIs: What to Expect.

Blood testing. Exposure history, staging, immunity

  • HIV antigen/antibody assays (fourth-generation screens with differentiation reflexes. Weeks-long windows).
  • Syphilis treponemal/non-treponemal cascade (exposure confirmation plus activity titers. Staging and cure verification across months).
  • Hepatitis B panels (susceptible, immune, acutely, chronically infected states from three markers).
  • Type-specific herpes serology (limited screening role. Site-blind, timing-blind, false-positive-prone).

Blood tests answer different questions than NAAT (history, staging, immunity) on longer timelines.

Detail at Blood Tests for STIs: What They Detect.

Site-specific logic. The coverage rule stated once

  • Oral exposure → throat swab plus blood tests.
  • Anal exposure → rectal NAAT plus blood tests.
  • Genital symptoms → genital sample plus blood tests.
  • Sores → sore swabs plus blood tests.
  • Pregnancy → blood panels plus NAAT per schedule.

Describe all exposure sites honestly so sampling covers them. Undisclosed sites go unsampled, and unsampled sites stay undiagnosed.

“Full panel” means this combination matched to your history, never one cup or tube.

When to seek care

When any site was exposed, when symptoms localize somewhere (sore throat, rectal pain), for routine panels covering all relevant sites, and during pregnancy per screening schedules.