Should a patient with Sjögren's syndrome undergo lactate testing and kidney function tests (KFT/RFT), including renal function tests (RFT) and kidney function tests (KFT)?

From the Guidelines

Yes, patients with Sjögren's syndrome should undergo both lactate testing and kidney function tests (KFT/RFT). Monitoring lactate levels is important because Sjögren's patients can develop metabolic abnormalities and lactic acidosis, particularly if they have associated conditions like interstitial lung disease or are taking medications that affect metabolism. Kidney function testing is essential because Sjögren's syndrome can cause renal involvement in 5-10% of patients, including tubulointerstitial nephritis, glomerulonephritis, or renal tubular acidosis. A comprehensive kidney profile should include serum creatinine, blood urea nitrogen (BUN), estimated glomerular filtration rate (eGFR), electrolytes (sodium, potassium, chloride, bicarbonate), and urinalysis to check for proteinuria or hematuria. These tests should be performed at diagnosis and then regularly during follow-up visits, typically every 6-12 months or more frequently if abnormalities are detected. Early detection of kidney involvement allows for timely intervention to prevent progression to chronic kidney disease, which can significantly impact prognosis and quality of life in Sjögren's patients 1.

Some key points to consider:

• The European League Against Rheumatism (EULAR) has developed recommendations for the management of patients with Sjögren's syndrome, including the use of topical and systemic therapies 1.
• Patients with Sjögren's syndrome should be evaluated for pulmonary disease, including interstitial lung disease, and monitored regularly for signs of disease progression 1.
• The use of corticosteroids and immunosuppressive agents, such as azathioprine and mycophenolate mofetil, may be necessary to manage pulmonary disease in patients with Sjögren's syndrome 1.
• Regular monitoring of kidney function and lactate levels is essential to prevent long-term complications and improve quality of life in patients with Sjögren's syndrome.

Key recommendations:

• Perform lactate testing and kidney function tests (KFT/RFT) at diagnosis and regularly during follow-up visits.
• Monitor patients for signs of disease progression, including pulmonary disease and kidney involvement.
• Use corticosteroids and immunosuppressive agents as needed to manage pulmonary disease.
• Regularly assess kidney function and lactate levels to prevent long-term complications.

From the Research

Renal Involvement in Primary Sjögren's Syndrome

• Primary Sjögren's syndrome (pSS) is a chronic autoimmune disorder that can affect multiple organs, including the kidneys 2, 3, 4, 5, 6.
• Renal involvement in pSS is a frequent extraglandular manifestation, affecting approximately 5-10% of patients 4, 5.
• The most common form of nephropathy in pSS is tubulointerstitial nephritis (TIN), characterized by lymphoplasmacytic infiltration of the kidney 3, 5.

Laboratory Tests for Renal Involvement

• Patients with pSS should undergo regular screening for renal involvement, including urinalysis, serum creatinine, and kidney function tests (KFT) or renal function tests (RFT) 3, 5.
• Lactate levels may not be directly relevant to renal involvement in pSS, but electrolyte disturbances such as renal tubular acidosis can occur 2, 5.
• A water deprivation test and an oral ammonium chloride loading test may be performed to assess urine concentrating capacity and acidification ability 2.

Treatment and Outcome

• Treatment for kidney disease in pSS is guided by the pattern of disease, with immunosuppression and electrolyte imbalance correction commonly used for TIN 4, 6.
• Glomerular disease is less common and typically involves an immune complex-mediated process, with treatment targeted to the histological pattern 3, 6.
• The risk of end-stage kidney disease is low, but patients with pSS and kidney disease have significantly reduced quality of life 4.