Serum procalcitonin has negative predictive value for bacterial infection in active systemic lupus erythematosus.
BACKGROUND
Previous studies in systemic lupus erythematosus (SLE) patients have produced conflicting results regarding the diagnostic utility of procalcitonin (PCT). The aim of this study was to determine predictive values of PCT and C-reactive protein (CRP) for bacterial infection in SLE patients.


METHODS
This was a cross-sectional study of clinic and hospitalized SLE patients with and without bacterial infection recruited over 18 months. Bacterial infection was defined as positive culture results. SLE disease activity was measured using SLEDAI. PCT and CRP were measured by automated immunoassays.


RESULTS
Sixty-eight patients (57 females) were studied. Ten patients (15%) had infection. The areas under the receiver operating characteristic curves for PCT and CRP were not significantly different [0.797 (CI 0.614-0.979) versus 0.755 (CI 0.600-0.910)]. In lupus flare patients, PCT but not CRP was higher with infection (p = 0.019 versus 0.195). A PCT of <0.17 ng/ml ruled out infection with 94% negative predictive value (NPV). In remission patients, CRP but not PCT was elevated with infection (p = 0.036 versus 0.103). CRP < 0.57 mg/dl had 96% NPV.


CONCLUSIONS
PCT may be a better marker to rule out bacterial infection in lupus flare but not in remission or general screening.
Department of Pathology, Faculty of Medicine, Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia. khalidah@ppukm.ukm.my
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Bador
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Intan
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Hussin
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Gafor
D000293:Adolescent; D000328:Adult; D001331:Automation; D001424:Bacterial Infections / Q000175:diagnosis* / Q000209:etiology; D002097:C-Reactive Protein / Q000378:metabolism*; D002116:Calcitonin / Q000097:blood*; D015740:Calcitonin Gene-Related Peptide; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods; D008180:Lupus Erythematosus, Systemic / Q000150:complications* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011498:Protein Precursors / Q000097:blood*; D012372:ROC Curve; D012720:Severity of Illness Index; D055815:Young Adult
C000606589:CALCA protein, human; D011498:Protein Precursors; D002116:Calcitonin; D002097:C-Reactive Protein; D015740:Calcitonin Gene-Related Peptide