Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (833 page)

   Gonococcal arthritis

   Pitfalls

Complement activity is unstable and heat-labile, and it is reduced after a few hours in samples kept at room temperature. Serum samples should not be kept at room temperature for more than 6 hours or refrigerated for more than 7 days prior to analysis.

   Specimens left to
clot
at refrigerated temperature lose activity because of complement activation.

   Complement components deteriorate in samples that are repeatedly thawed and frozen.

   Severe hemolysis, lipemia, or bilirubinemia may interfere with accurate measurement.

Complement Components in Plasma and Their Deficiencies
*

*
Modified from Massey HD, McPherson RA. In:
Henry’s Clinical Diagnosis and Management by Laboratory Methods
, Table 47-3, p.920, and Table 47-4, p.921 22nd ed. Saunders, 2011.

Suggested Readings

Botto M, Kirshfink M, Macor P, et al. Complement in human diseases: lessons from complement deficiencies.
Mol Immunol.
2009;46:2774–2783.

Nester CM, Thomas CP. Atypical hemolytic uremic syndrome: what is it, how is it diagnosed, and how is it treated?
Hematology Am Soc Hematol Educ Program.
2012;2012:617–625.

COMPLETE BLOOD COUNT (CBC)
*

   Definition

   CBC is a numerical report of all blood elements, as well as a description of some of their major characteristics. Most laboratories use automated counters. The CBC reports include RBC count, WBC count, platelet count, Hb, Hct (volume of packed red cells), mean platelet volume, and other parameters (described under individual tests). The CBC may be ordered as a simple count of blood elements and RBC indices or as a test that includes a WBC differential.

   Use

   CBC is used for screening whenever abnormalities in RBCs, WBCs, or platelets are suspected.

   New analyzers may separate reticulocytes and platelets into young and mature populations that help detect bone marrow regeneration. Automated counters flag abnormalities in RBCs, WBCs, and platelets, triggering examination of the peripheral blood smear.

   Limitations