Test result	When to order	Associated diseases/conditions
Elevated antineutrophil cytoplasmic antibody, antiglomerular basement membrane antibody	Suspected acute glomerulonephritis, pulmonary renal syndromes	Vasculitis, Goodpasture syndrome
Elevated antistreptolysin O titer	Recent infection and clinical picture of acute glomerulonephritis	Poststreptococcal glomerulonephritis
Elevated creatine kinase level, elevated myoglobin level, dipstick positive for blood but negative for red blood cells	Recent trauma, muscle injury	Rhabdomyolysis
Elevated prostate-specific antigen level	Older men with symptoms suggestive of urinary obstruction	Prostate hypertrophy, prostate cancer
Elevated uric acid level	History of rapidly proliferating tumors, recent chemotherapy	Malignancy, tumor lysis syndrome
Eosinophiluria	Fever, rash	Allergic interstitial nephritis
Evidence of hemolysis (schistocytes on peripheral smear, decreased haptoglobin level, elevated indirect bilirubin level, elevated lactate dehydrogenase level)	Fever, anemia, thrombocytopenia, neurologic signs	Hemolytic uremic syndrome, thrombotic thrombocytopenic purpura, systemic lupus erythematosus, other autoimmune diseases
Hydronephrosis on renal ultrasonography	Suspected obstruction	Malignancy, prostate hypertrophy, uterine fibroids, nephrolithiasis, ureterolithiasis
Increased anion gap with increased osmolar gap*	Suspected poisoning, unresponsive patient	Ethylene glycol or methanol poisoning
Low complement level	Suspected acute glomerulonephritis	Systemic lupus erythematosus, endocarditis, postinfectious glomerulonephritis
Monoclonal spike on serum protein electrophoresis	Anemia, proteinuria, acute kidney injury in older patients	Multiple myeloma
Positive antinuclear antibody, double-stranded DNA antibody	Proteinuria, skin rash, arthritis	Autoimmune diseases, systemic lupus erythematosus
Positive blood cultures	Intravenous drug use, recent infection, new cardiac murmur	Endocarditis
Positive HIV test	Risk factors for HIV infection	HIV nephropathy