Application of leukocyte esterase strip test in the screening of periprosthetic joint infections and prospects of high-precision strips

Role of α-Defensin and the Microbiome in Prosthetic Joint Infection: A Prospective Cohort Study in Korea

The utility of α-defensin (AD), leukocyte esterase (LE) levels, and metagenomics sequencing as diagnostic tools for prosthetic joint infection (PJI) has been suggested, but there are few studies among the Asian population. This study aimed to evaluate the diagnostic performance of various biomarkers for PJI and the role of the microbiome in the synovial fluid of patients with prostheses. Patients with suspected knee PJI were enrolled, and their blood and synovial fluid were collected. The cases were classified into the PJI and non-PJI groups. Significant differences between the two groups were observed in the levels of AD (4698 µg/L vs. 296 µg/L, p < 0.001) and positivity for LE (62.5% vs. 21.1%, p = 0.01). AD had 94.4% sensitivity and 89.5% specificity for diagnosing PJI, whereas LE had 37.5% sensitivity and 100% specificity. Microbiome taxonomic profiling showed high sensitivity. The number of operational taxonomic units and the richness of the microbiome in the synovial fluid were higher in the non-PJI than in the PJI group. AD has shown encouraging results in the Asian population as a diagnostic biomarker for PJI, and LE can be used as a diagnostic adjunct. The bacterial richness of the synovial fluid is likely associated with infections.

Atypical Presentation of Periprosthetic Joint Infection With Pseudotumor With a Modular-Neck Stem Implant

A 64-year-old male with a recalled modular-neck stem implant presented with a soft tissue mass in the lateral thigh. Preoperative testing revealed no signs of infection by the 2018 periprosthetic joint infection criteria. MRI revealed a large soft tissue mass around the implant consistent with a pseudotumor, and we performed revision surgery of the femoral component for trunnionosis. One intraoperative culture was positive for infection, and the patient was placed on antibiotics. Six weeks following revision surgery of the femoral component, the patient presented with acute drainage and was diagnosed with an acute on chronic periprosthetic joint infection and underwent explantation of the femoral and acetabular components with the placement of an antibiotic spacer. Cultures revealed identical bacteria from the index procedure. Given the clinical course, this case likely represents adverse local tissue reaction with an atypical presentation of periprosthetic joint infection. This is the first case presentation of an adverse local tissue reaction and superimposed periprosthetic joint infection with normal infection workup, representing an important consideration when differentiating between pseudotumor and periprosthetic joint infection in modular-neck femoral stem implants.

Fecal Leukocyte Esterase, an Alternative Biomarker to Fecal Calprotectin in Inflammatory Bowel Disease: A Pilot Series

Background and Aims

Fecal calprotectin (FC) is a noninvasive biomarker used in inflammatory bowel disease (IBD) management and risk stratification of nonspecific gastrointestinal symptoms. Leukocyte esterase is an inexpensive and widely available point-of-care inflammatory marker present on urinalysis test strips. We aim to assess the diagnostic accuracy of fecal leukocyte esterase (FLE) relative to FC and endoscopy and demonstrate its use as an alternative biomarker for IBD.

Methods

In this prospective cohort study, 70 patients who had FC ordered as part of standard clinical care also received FLE testing. FLE levels were compared with various FC cutoff values and endoscopy and pathology findings as the gold standard.

Results

As the FC cutoff increased from 50 to 500 μg/g, FLE sensitivity increased from 67% to 95% while the specificity decreased from 86% to 76%. The area under the receiver operating characteristic (AUROC) curve increased from 0.79 to 0.90. An FLE of ≥1+ had the best test characteristics. Among patients who underwent endoscopic evaluation, FLE demonstrated an identical sensitivity (75%) and specificity (86%) to FC in predicting endoscopic inflammation. AUROC was 0.80 for FLE and 0.85 for FC with an optimal cutoff of ≥2+ and 301 μg/g, respectively. When used to distinguish between patients with active IBD and no/inactive IBD, FLE had a sensitivity of 84% and specificity of 90%, comparable with the 84% and 83%, respectively, of FC. AUROC was 0.88 for FLE and 0.91 for FC with an optimal cutoff of ≥2+ and 145 μg/g, respectively.

Conclusion

FLE demonstrates adequate correlation and comparable accuracy with FC in predicting endoscopic inflammation and distinguishing between patients with active vs inactive IBD.