Evaluation of cerebrospinal fluid (CSF) C-reactive protein in the diagnosis of suspected meningitis

C-reactive protein and bacterial meningitis: a meta-analysis

The aim of the study was to review published articles on the diagnostic accuracy of C-reactive protein (CRP) tests with cerebrospinal fluid and serum in diagnosing bacterial meningitis. The literature from 1980 and onwards was searched using the electronic databases of MEDLINE, and we used summary receiver operating characteristic curve analyses (SROCs) to describe central tendencies and examine possible sources of inter-study variability in the results. We included data from 35 studies of both children and adults: 21 in which CRP had been measured in cerebrospinal fluid, 10 in which CRP had been measured in serum, and 4 in which it had been measured in both cerebrospinal fluid and serum. The odds ratio for bacterial meningitis versus aseptic meningitis for a positive CRP test with cerebrospinal fluid was estimated at 241 (95% confidence interval [CI]: 59-980), and the central tendencies for the true-positive fraction (sensitivity) and the false-positive fraction (1-specificity) were estimated at 0.94 and 0.06, respectively. The corresponding figures for a CRP test with serum were 150 (95% CI: 44-509), 0.92 and 0.08, respectively. Regression analyses including variables coding for study design features, inclusion of neonatal patients, geographical region, or use of a quantitative biochemical method did not indicate statistically significant contributions to inter-study variances in the log odds ratios. For values of the true- and the false-positive fractions of 0.92-0.94 and 0.06-0.08, respectively, the post-test probability of not having bacterial meningitis given a negative test is very high (> or = 97%), in the range of a pre-test probability (prevalence of bacterial meningitis) from 10 to 30%, whereas the post-test probability of bacterial meningitis given a positive test is considerably lower. Hence, only a negative test is highly informative in a typical clinical setting. This, as well as the absence of analyses to show if CRP tests contribute independent diagnostic information, relatively to the information held in the traditionally used clinical and biochemical variables, makes it difficult to conclude on the clinical usefulness of CRP tests in the management of patients suspected of having bacterial meningitis.

Acute phase proteins in serum and cerebrospinal fluid in the course of bacterial meningitis

We carried out estimations of the following acute phase proteins: C-reactive protein (CRP), alpha-1-antitrypsin (AAT), alpha-1-acid glycoprotein (AAG), alpha-2-ceruloplasmin (CER), and alpha-2-haptoglobin (HPT) in serum and in cerebrospinal fluid (CSF) in patients with bacterial meningitis (BM, n = 30) and viral meningitis (VM, n = 30). We have shown that determinations of concentrations of AAG and CRP in serum and CER in CSF are useful in differentiation between BM and VM. The diagnostic power of these three tests (the areas under their ROC curves equal 0.942, 0.929, and 0.931, respectively) is bigger, though statistically not significantly, than that of traditional parameters of BM in CSF, i.e., total protein concentration and white blood cell count. Determination of AAG, CRP, and AAT in serum is a valuable monitoring marker in the course of BM treatment. Convenience of serum sampling constitutes an advantage over traditional BM parameters in CSF.

C-reactive protein: a critical review

We have reviewed the literature to determine the value of C-reactive protein (CRP) measurements in the diagnosis and management of a wide range of conditions. CRP levels are of value in 6 clinical situations: (a) monitoring the response to antibiotic treatment in patients with known bacterial infections, (b) in obstetric patients with premature rupture of membranes, a rise in CRP can give early warning of intrauterine infections, (c) differentiation between active disease and infections in patients with systemic lupus and ulcerative colitis where the level of response to active disease has been previously established, (d) as a measure of disease activity and response to disease-modifying drugs in rheumatoid arthritis, (e) early detection of complications in postoperative patients, (f) in differentiating between infection and graft-versus-host-disease in bone marrow transplant patients. CRP levels have been used in an attempt to differentiate between bacterial and viral infections in various clinical situations, however the published literature does not support this role.

C-reactive protein and bacterial meningitis

We have studied prospectively the C-reactive protein values in the cerebrospinal fluid of 54 patients with bacterial meningitis, tuberculous meningitis, and severe malarial infection and convulsions without infections of the central nervous system. CSF CRP above 1 mg/l was observed in 23 out of 28 patients with bacterial meningitis (sensitivity of 82%). The specificity was 73% at the 1 mg/l level. Five out of 19 patients with severe malarial infection had CSF CRP levels above 1 mg/l. Two patients with TB meningitis were also studied. Both of them had CSF CRP above 1 mg/l. Five patients with febrile convulsions or sepsis without meningitis had CSF CRP below 1 mg/l. It is concluded that CSF CRP would not be used as a useful discriminatory test in areas where malaria and TB meningitis are common.

Quantitation of C-reactive protein in cerebrospinal fluid and serum by zone immunoelectrophoresis assay (ZIA)

The zone immunoelectrophoresis assay (ZIA) for C-reactive protein (CRP) determinations is easy to perform and requires only small amount of antiserum, e.g., 25-100 and 0.5-1.0 microliter anti-CRP antibody/20 serum and CSF samples, respectively. For quantitating CSF-CRP the immunoprecipitates formed were stained using alkaline phosphatase-conjugated secondary antibodies and the lowest standard concentration used was 30 micrograms/l. The immunoprecipitates formed when measuring CRP in serum were stained by Coomasie brilliant blue R250 with a detection limit of about 300 micrograms/l. CRP was determined in cerebrospinal fluid in 27 patients with bacterial meningitis (range less than 0.03-23.0 mg/l) and in 25 patients with viral meningitis (range less than 0.03-0.23 mg/l). CRP was quantitated in 52 sera by both the CRP ZIA method (y) and by electroimmunoassay (x). The correlation coefficient was r = 0.992 with the regression line y = 1.024 x + 0.855.