They help rule out other potential causes of renal failure.
Auto-immune diseases such as systemic lupus erythematosus
commonly cause renal failure. They may show evidence of active inflammation such as
increased erythrocyte sedimentation rate and decreased serum
complement (the latter in inflammatory conditions where complement
is activated and thus consumed). Lupus also frequently produces anti-nuclear antibodies,
which were not seen in this case. IgA nephropathy may also produce renal failure,
and may be accompanied by increased levels of IgA. Finally, some forms of
renal failure are hereditary and thus the absence of a family history is an
important negative as well.