A Diagnostic Accuracy Study of Combined OMP22-PCR and SAT for Brucellosis in Xinjiang, China.

BACKGROUND

The standard tube agglutination test (SAT) is a cornerstone for brucellosis diagnosis but has inherent limitations, including false negatives in early and chronic infections and false positives due to cross-reactivity. To overcome these drawbacks, molecular detection targeting the highly conserved Brucella outer membrane protein 22 (OMP22) gene presents a promising solution. This study aimed to evaluate the diagnostic value of OMP22-PCR and its efficacy when combined with SAT.

METHODS

From January 2023 to May 2024, serum samples from 62 culture-confirmed brucellosis patients and 25 controls were analyzed using OMP22-PCR and SAT. Diagnostic performance was compared, discordant results were analyzed, and OMP22 detection was extended to 20 clinical isolates, 20 urine samples, and 2 cerebrospinal fluid (CSF) samples.

RESULTS

OMP22-PCR demonstrated a sensitivity of 93.5% and specificity of 92.0%, which was comparable to SAT (96.8% and 88.0%, respectively; both P > 0.05). Crucially, the combined detection approach achieved a significantly higher specificity of 100% and a positive predictive value of 100%, and a significantly larger area under the ROC curve (AUC) than either test alone (P < 0.05), all while maintaining a high sensitivity of 96.8%. Analysis of discordant samples revealed their complementary nature: SAT-positive/OMP22-PCR-negative samples were primarily from chronic-stage patients, whereas SAT-negative/OMP22-PCR-positive samples were from early-stage patients. Furthermore, OMP22 was detected in all clinical isolates (100%), 70.0% of urine samples, and both CSF samples (100%).

CONCLUSION

The combination of OMP22-PCR and SAT effectively compensates for the limitations of each method alone, significantly enhancing diagnostic accuracy. The strong performance of OMP22-PCR in non-blood samples further underscores its value as a complementary tool, thereby supporting the development of more comprehensive diagnostic strategies for brucellosis.