Hi,
Double stranded DNA is a blood test that makes a definite lupus diagnosis. This along with low complement levels, specifically C3 and C4 often correlate to kidney involvement.
There are many test results that can give the doctor information on ones kidneys...urinalysis looking for protein, blood, and cast cells. When this is present there may be active kidney inflammation going on. The only way to know for sure what is going on is by a kidney biopsy.
One's hemoglobin, total protein, serum albumin can also be low when there is active inflammation in the kidneys. Your serum creatinine may increase above normal range...although this does not always need to occur.
Your doctor will order a 24 hour urine if she want more specific information on the overall functioning of the kidneys. You do not feel kidney inflammation which is why the doctors have various blood/urine tests that they order.
If I can be of any further help, please don't hesitate to ask. I have kidney disease from lupus. Best of Luck!