Cross-validation of the Invalid Forgetting Frequency Index (IFFI) from the Test of Memory Malingering

Abstract

Objective: To increase sensitivity of the Test of Memory Malingering (TOMM), adjustments have been proposed, including adding consistency indices. The Invalid Forgetting Frequency Index (IFFI) is the most recently developed consistency index. While strong classification accuracy rates were originally reported, it currently lacks cross-validation.

Method: A sample of 184 outpatients was utilized. Valid performers passed all criterion performance validity tests (PVTs) and invalid performers failed two or more PVTs. Classification accuracy statistics were calculated.

Results: AUC for the IFFI was 0.80, demonstrating adequate discrimination between valid and invalid groups. A score of 3 or more inconsistent responses resulted in sensitivity and specificity rates of 63% and 92%, respectively.

Conclusions: This is the first article to cross-validate the IFFI. In both the original IFFI study and the current study, the same cut-off was found to maintain at least 90% specificity while producing higher sensitivity rates than those achieved by traditional TOMM indices.

Keywords: Cross-validation; IFFI; Invalid Forgetting Frequency Index; TOMM; Test of Memory Malingering.