Qualitative and Quantitative Analysis of C-Reactive Protein in Inflammatory and Infectious Conditions

Abstract

Background: C-Reactive Protein (CRP) is a key biomarker for inflammation and infection, widely used in clinical settings to assess disease severity and monitor therapeutic responses. Qualitative and quantitative CRP tests serve distinct diagnostic purposes, with the former offering rapid screening and the latter providing precise measurements. This study evaluates the diagnostic utility of both methods in inflammatory and infectious conditions, comparing their accuracy, feasibility, and clinical applicability.

Methods: A cross-sectional study was conducted over 8 months at Saidu Teaching Hospital, Pakistan, involving 150 patients with suspected inflammatory or infectious diseases. Venous blood samples were analyzed using qualitative (latex agglutination) and quantitative (immunoturbidimetric) CRP tests. Diagnostic accuracy, sensitivity, specificity, and correlations with other inflammatory markers (WBC count, ESR) were assessed using SPSS version 25.

Results: Qualitative CRP testing showed 80.4% sensitivity and 78.9% specificity, with a diagnostic accuracy of 80%. However, its negative predictive value (NPV) was limited (57.7%). Quantitative CRP testing identified elevated levels (>5 mg/L) in 74.7% of patients and demonstrated strong correlations with ESR (r = 0.75) and WBC count (r = 0.62). Significant agreement was observed between the two methods (χ² = 45.2, p < 0.001).

Conclusion: Qualitative CRP testing is a cost-effective screening tool, particularly in resource-limited settings, but lacks precision for mild or early-stage inflammation. Quantitative CRP testing offers superior accuracy for disease stratification and treatment monitoring. The complementary use of both methods can enhance diagnostic efficiency, with qualitative tests for initial triage and quantitative tests for detailed evaluation in complex cases.