Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1132 page)

   Severe functional platelet defects

   Rapid preoperative evaluation of patients with a bleeding history

   Useful in detecting the effect of therapy with DDAVP (desmopressin acetate)

   To detect improved hemostasis after platelet transfusions

   Limitations

   In vitro assays often do not detect mild platelet abnormalities.

   The in vitro results have a good negative (rule out) predictive value in cases with low or intermediate suspicion for a hemostatic defect. If, however, the results with the in vitro assay are negative, but the clinical suspicion of a hemostatic defect is strong, more definitive studies are recommended (platelet aggregation assays or vWF panels [see p. 454]).

   If the results are positive, additional studies (platelet aggregation and/or vWF panels) are recommended for a definitive diagnosis.

   Several factors are known to effect in vitro platelet assays such as hematocrit and white cell count. Correction factors may need to be applied to ensure correct interpretation.

Suggested Readings

Bonello L, Tantry U, Marcucci R, et al. Consensus and future directions on the definition of high ontreatment platelet reactivity to adenosine diphosphate.
J Am Coll Cardiol.
2010;56:919–933.

Kakouros N, Kickler TS, et al. Hematocrit alters VerifyNow P2Y12 assay results independently of intrinsic platelet reactivity and clopidogrel responsiveness.
J Thromb Haemost.
2013;1:1–9.

PLEURA, NEEDLE BIOPSY (CLOSED CHEST)

   Definition

   Pleural diseases involve the parietal and visceral pleura and can be either inflammatory or malignant origin, resulting in pleural effusion. A needle biopsy of the pleura is performed to evaluate and exclusion of infectious etiologies such as tuberculosis malignant disease. Various biopsy techniques are available to diagnose pleural disease. The newer techniques include image-guided and thoracoscopic biopsy provide better diagnostic accuracy.

   Use (see Chapter
13
, “Respiratory, Metabolic and Acid–base Disorders,” for more information about pleural effusions)