P63
IS ROUTINE MEASUREMENT OF SERUM COMPLEMENT HELPFUL?
Brown, R A*, Choa, R, Howse, M L P Williams, P S
Royal Liverpool University Hospital
Hypocomplementaemia is associated with important renal diagnoses. Does routine
measurement aid diagnosis?
METHODS: Complement samples taken by the nephrology department of a university
teaching hospital 2001-5 were analysed. Low levels were correlated with clinical diagnosis
using computerised records.
RESULTS: There were 4230 measurements of C3 and C4 in 3002 patients. Mean age was
62.4y, 55.4% were male. There were 812 samples in 471 patients in which either or both C3 and
C4 were below normal range.
Analysis of patient s first low complement result.
DIAGNOSIS
SLE
MPGN
Post Strep GN
Sepsis
Cryoglobulinaemia
ANCA+ GN
Other GN
Other
No Diagnosis
C3
0
0
0
5
0
2
3
16
10
INPATIENTS
C4 C3&C4 % of total
4
4
4.8
1
0
0.6
0
0
0
2
6
7.9
1
0
0.6
2
4
4.8
4
4
6.7
24
9
29.7
47
17
44.9
C3
2
5
0
0
0
0
2
11
6
OUTPATIENTS
C4
C3&C4 % of total
35
18
18.0
12
2
6.2
1
1
0.7
4
0
1.3
2
0
0.7
5
1
2.0
20
1
7.5
99
13
40.2
63
3
23.5
The positive predictive value of low C3 and C4 for a well described diagnostic association was
weak: in-patient (13%), clinic (27%), the overwhelming majority had a diagnosis not usually
associated with low C3/4 or had undiagnosed minor renal lesion.
There was no relationship between severity of hypocomplementaemia and diagnostic groups.
A well described diagnostic association was not associated with more profound
hypocomplementaemia. (See figure)
Complement g/L
Mean C3 and C4 levels and diagnosis
C3
C4
1.00
0.80
0.60
0.40
0.20
0.00
SLE
Cresentic GN
MPGN
Other GN
Sepsis
Other
Unexplained
CKD
Diagnosis
CONCLUSION: Our results suggest isolated hypocomplementaemia may have little clinical
significance and routine, indiscriminate testing is unrewarding.