American Board of Internal Medicine (ABIM) Certification Practice Exam

What is required to confirm and classify the diagnosis of lupus nephritis?

1. Blood test

2. Kidney biopsy

3. Urinalysis

4. CT scan

The correct answer is: Kidney biopsy

To confirm and classify the diagnosis of lupus nephritis, a kidney biopsy is essential. Lupus nephritis is a serious renal complication associated with systemic lupus erythematosus (SLE), and it can manifest in various forms with differing histological characteristics. A kidney biopsy allows for direct examination of renal tissue, which helps identify specific changes such as immune complex deposition, glomerular inflammation, and fibrosis, facilitating accurate classification according to the standard histopathological classifications, such as the World Health Organization (WHO) criteria. While blood tests can provide information on kidney function and the presence of autoantibodies associated with SLE, and urinalysis can reveal abnormalities like proteinuria or hematuria indicative of nephritis, neither are definitive for confirming the presence or type of lupus nephritis. Similarly, CT scans are useful for imaging purposes but do not offer the histological details necessary for diagnosis and classification. Therefore, the kidney biopsy stands out as the critical procedure needed to confirm the diagnosis and categorize the specific type of lupus nephritis a patient may have.