Pernicious Anemia: Likelihood Ratios

Introduction: Autoimmune attack of the parietal cells in the stomach that are responsible for producing intrinsic factor. Intrinsic factor is necessary for the absorption of vitamin B12 (cobalamin), thus its loss causes Megaloblastic Anemia.

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The likelihood ratios of findings for Pernicious Anemia 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
[ + ] Anti-parietal Cell Antibody	+ 0 -	8.5	0.2
Study: Arch Intern Med. 1999 Jun 28;159(12):1289-98. PMID: 10386505

Poorly Diagnostic Findings
Finding	Result	+LR	-LR
[ + ] Elevated Fasting Serum Gastrin		Sensitivity = 90%
>200ng/L. Specificity not assessed. Study: Arch Intern Med. 1999 Jun 28;159(12):1289-98. PMID: 10386505 Am J Clin Pathol. 1988 Oct;90(4):442-5. PMID: 3177265
[ + ] Anti-Intrinsic Factor Antibodies		Sensitivity = 50%
Specificity not mentioned but given as "rarely present in healthy individuals". Some people with Graves + anti-IF may progress to pernicious anemia. Study: Arch Intern Med. 1999 Jun 28;159(12):1289-98. PMID: 10386505