Henoch-Schonlein Purpura: Likelihood Ratios

Introduction: an autoimmune vasculitis affecting primarily children, classically presenting with: palpable purpura, abdominal pain, renal failure, and arthritis.

The purpura classically present on the lower extremities and buttocks.

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Tags: Autoimmune Pediatrics Renal Vasculitis Tag this Diagnosis.

The likelihood ratios of findings for Henoch-Schonlein Purpura are listed below. See the left navigation bar to change the display.

Pre-Test Probability (Prevalence): %.	Post-Test Probability (Predictive Value): %.	Switch to display mode.
Note that calculating probabilities from more than one** finding is inherently inaccurate because findings are not independent. (For example, using two positive findings that share a common pathogenesis is likely to overestimate the true probability.)

Good Positive and Negative Likelihood Ratios
Finding	Result	+LR	-LR
[ + ] ACR Criteria	+ 0 -	7.1	0.1
>=2 of 4: patient 20 years or younger at onset, palpable purpura (without thrombocytopenia), bowel angina (diffuse abdominal pain or diagnosis of bowel ischemia), and histologic changes showing granulocytes in small walls of arterioles and venules (leukocytoclastic vasculitis) Note that the criteria have since been revised to make palpable purpura a mandatory feature, remove the age criterion, add arthritis as a criterion, and replace granulocytes in biopsy specimens with IgA deposition. However, the new criteria have not been validated. Study: Am Fam Physician. 2009 Oct 1;80(7):697-704. PMID: 19817340

Poorly Diagnostic Findings
Finding	Result	+LR	-LR
[ + ] Arthritis		Sensitivity = 75%
nonmigratory polyarthritis Study: Am Fam Physician. 2009 Oct 1;80(7):697-704. PMID: 19817340
[ + ] Upper Respiratory Tract Infection		Sensitivity = 50%
antecedent to the HSP presentation Study: UpToDate http://www.utdol.com/online/content/topic.do?topicKey=pedirheu/12789