# Discordant Vitamin B12 Results in an IgA Nephropathy Patient

## TL;DR

A patient with IgA nephropathy had misleadingly high Vitamin B12 levels due to immunoassay interference, highlighting the need for careful interpretation and additional testing.

## Contribution

Demonstrates the use of PEG precipitation as a practical method to detect macro-VitB12 interference in clinical labs.

## Key findings

- Elevated Vitamin B12 levels were due to macro-VitB12, not actual deficiency or excess.
- PEG precipitation effectively identified the interference, avoiding unnecessary investigations.
- Clinical correlation is essential when Vitamin B12 results conflict with patient history.

## Abstract

Discordant Vitamin B12 results can result from immunoassay interferences, potentially leading to unnecessary diagnostic procedures and misdiagnoses if not properly recognized.

A 76‐year‐old male with a history of IgA nephropathy, hypertension, and other comorbidities presented with unexpectedly elevated total Vitamin B12 levels despite no supplement use and normal hematological and biochemical parameters. Polyethylene glycol (PEG) precipitation demonstrated markedly reduced recovery, indicating the presence of macro‐VitB12. Pretreatment with blocking reagents and exclusion of heterophilic antibodies confirmed the interference. The discrepancy observed between analytical platforms further supported this finding.

Vitamin B12 results should always be interpreted in conjunction with clinical findings. Polyethylene glycol (PEG) precipitation is a cost‐effective and accessible method for detecting macro‐VitB12, particularly in cases where analytical results are inconsistent with the clinical presentation.