Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1417 page)

   
Expected results:
Negative.

   
Positive results:
A positive result establishes a diagnosis in patients with compatible symptoms and risk for STD. Positive results must be interpreted with caution in patients with low risk for STD. Repeat testing, ideally performed on a repeat specimen using a different test platform or target sequence, is recommended if a false-positive result is suspected.

   
Negative results:
Infection is unlikely. Poor collection technique, low target levels, or other factors may cause false-negative results.

   Limitations

   
Common pitfalls:
Test results must be interpreted in the context of the clinical impression and prior probability of infection. Repeat testing should be performed if false-positive or false-negative test results are suspected.

   There is significant overlap in the signs and symptoms of these and other urogenital infections, like bacterial vaginitis, or noninfectious conditions. Laboratory testing for these STIs does not replace physical examination and other testing appropriate for the patient’s presentation.

   Accuracy depends on proper specimen collection: the use of incorrect swabs for specimen collection, improper filling of urine transport tubes, and submission of inappropriate specimen types may result in false-negative results.

   Amplified nucleic acid tests should not be used for test of cure evaluations (within 4 weeks of treatment), because DNA may be detectable even after viable organisms have been eliminated.

   Other Considerations

   As part of routine quality assurance practices, laboratories that perform amplified nucleic acid tests should routinely perform “wipe tests” of surfaces in the laboratory where NAATs are performed, and perform further evaluation and maintenance according to the test manufacturer’s instructions. Laboratories should also monitor their reported rates of
C
.
trachomatis
,
N
.
gonorrhoeae
, and
T
.
vaginalis
infections; increasing positivity rates not explained by changes in patient populations tested may be an indication of laboratory contamination; careful evaluation of laboratory procedures should be performed.

SPUTUM CULTURE (ROUTINE)

   Definition

   Lower respiratory tract (LRT) infections may involve any of the anatomic areas inferior to the larynx. Infections include tracheobronchitis (large airway disease), bronchiolitis (small airway disease), and pneumonia (alveolar disease). The common etiologies depend on the site of infection, age and underlying health of the patient, season, and other factors.