Complete learning materials
Review each topic, apply the clinical case, then complete the linked ten-question assessment.
Selecting infectious tests
- Use exposure history, syndrome, symptom duration, vaccination and local prevalence to choose appropriate tests.
- Obtain cultures before antimicrobial therapy when feasible for severe infection, but never delay life-saving management.
- Distinguish infection from colonization: a positive test may not imply the organism causes symptoms.
Test characteristics and timing
- NAAT/PCR detects organism nucleic acid, which may persist after infectivity resolves; timing and specimen quality matter.
- Antibody tests can be negative early in infection and sometimes remain positive after prior infection or vaccination.
- A negative test does not reliably exclude disease when pretest probability is high and sensitivity depends on illness stage.
Autoimmune and inflammation tests
- ESR and CRP are nonspecific; interpret with symptoms and history instead of using them as stand-alone diagnoses.
- ANA has a substantial false-positive burden in low-risk populations; order with a compatible clinical syndrome.
- Use reflex or specific antibodies judiciously and understand that a positive screen alone is not a diagnosis.
Public health and consent
- Follow applicable local public-health reporting obligations and laboratory collection instructions; explain confidentiality limits.
- Use informed consent and pre/post-test counselling for sensitive testing as required by local policy.
- Use evidence-based screening recommendations; avoid ordering repeated serology without a meaningful clinical question.
Applied clinical case
Case: A patient with dysuria but no systemic illness needs symptom-directed urine testing; a positive urine culture without symptoms generally should not trigger antibiotics except in specific guideline-defined circumstances such as pregnancy.
Downloadable resources
Practice this lesson (10 questions)
Practice lesson questions