Immunocompetence of the severely injured spleen verified by differential interference contrast microscopy: the red blood cell pit test.

OBJECTIVE

To determine the immunocompetence of the successfully nonoperatively managed injured spleen warranting vaccinations for overwhelming postsplenectomy sepsis by differential interference contrast microscopy (DICM).

METHODS

Cull an urban Level I trauma systems data bank for all patients with grade IV or V splenic injuries (those with the greatest potential to compromise immunologic function) successfully managed nonoperatively and those who have required splenectomies since 1996 and verify the Association for the Surgery of Trauma grading. Contact or obtain written consent of these patients and acquire a blood sample for DICM (red blood cell [RBC] pit analysis) and IgM levels (as a control). Compare values of those sustaining splenic injuries with those of two control groups: patients with splenectomies and those with normal splenic function.

RESULTS

Forty patients were contacted, consented, and volunteered blood samples: 10 patients with grade IV splenic injuries, 1 patient with a grade V injury, 14 patients with splenectomies, and 15 controls. Average RBC pit levels and IgM levels for patients sustaining injuries (15) and successfully nonoperatively managed were 0.6% (0%-2% nL) and 91 mg/dL (46-304 nL), respectively. Patients with splenectomies had levels of 20.4% and 86 mg/dL whereas controls had levels of 0.7% and 110 mg/dL, respectively. The average time frame from injury to RBC pit test was 3.1 years. Comparing the successfully nonoperatively managed group with the splenectomy group using t test with Satterthwaite's method because of unequal variances, there was a statistically significant difference (p = 0.0002). Comparing the same study group with those with normal splenic function using t test with pooled variance, there was no statistical significant difference between groups (p = 0.489).

CONCLUSION

DICM, a commonly used test to evaluate splenic-based immunocompetence in patients with sickle cell anemia, hemoglobinopathies, and patients undergoing partial splenectomies, also confirms splenic immunocompetence in patients sustaining up to grade IV splenic injuries. IgM levels earlier thought to be low in patients after splenectomy normalize.