Semi-quantitative analysis of Streptococcus pneumoniae urinary antigen: Kinetics of antigen titers and severity of diseases

Abstract

Detection of urinary antigen by a rapid immunochromatographic membrane test (Binax NOW) was widely accepted as a powerful tool for diagnosis of Streptococcus pneumoniae pneumonia. This is a qualitative kit, so the value of quantitative analysis of urinary antigen, especially correlation of antigen titers and severity of diseases, remained to be determined. We examined semi-quantitative antigen titer in urines collected from urinary antigen-proven S. pneumoniae pneumonia on admission, and analyzed the kinetics of antigen titer and its relation to severity of diseases. After serial 2-fold dilution of urine, the highest dilution for positive results was determined, and this was designated as maximum dilution factor (MDF). MDFs varied from 1 to 4096 in 29 patients examined (mean MDF, 317.8). Importantly, severe cases of S. pneumoniae pneumonia were higher values of MDFs (mean MDF: 760.5) than those of non-severe cases (mean MDF: 5.4). The patients with high MDFs (> or = 64) demonstrated higher values of LDH, CRP and lower values of WBC and PaO2 compared to those of low MDFs group (< or = 32). There was no clear correlation between CRP values and antigen titers, and conversely the majority of severe cases showed relatively weak CRP responses, despite high levels of bacterial antigen. Kinetic analysis of urinary and serum antigen titers in 4 cases of S. pneumoniae pneumonia exhibited consistently higher values of antigen titers in urine than those in serum. The half lives of urinary and serum antigen titers were calculated to be 1.0-3.4 and 1.1-2.3 weeks, respectively. These data suggest that quantitative analysis of urinary antigen may be a useful indicator for severity of disease and course of S. pneumoniae pneumonia. Our results demonstrate an application for S. pneumoniae antigen titer determination in urine and serum, which may be crucial not only for diagnostic measures, but also may provide a better understanding of the pathogenesis of S. pneumoniae infection.

Reply to: “The application of urinary antigen test score in pneumococcal pneumonia in children”

“…However, the time to positive reaction and the intensity of reaction band were not influenced by the urinary gravity. The findings were also in agreement with a report by Tateda et al, 4 who suggested that the fold difference between severe and non-severe groups could not be achieved by urinary concentration under normal physiological status.…”

A new urinary antigen test score correlates with severity of pneumococcal pneumonia in children

“…The current findings demonstrate a significant correlation between the test score and disease severity. These observations are in accordance with those of Tateda et al 11 In their study, serial two-fold dilutions of urine were used for antigen testing, and the final dilution that was positive for antigen was recorded as the maximum dilution factor. They have noted that severe cases of S. pneumoniae pneumonia have higher values of maximum dilution factors than those with non-severe disease.…”

“…More recently, researchers have developed a new semi-quantitative urinary antigen test to correlate the kinetics of the antigen titers with disease severity. 11 It has been proposed that the amount of pneumococcal antigen present in the urine is related to the magnitude of the bacterial load in the lungs.…”

Diagnostic Usefulness of Ribosomal Protein L7/L12 for Pneumococcal Pneumonia in a Mouse Model

“…Other studies testing CAD kit sensitivity and specificity in blood cultures reported a range of 79 to 87% for sensitivity and a range of 83 to 97% for specificity (17,28,31). While these detection rates are high, the CAD kit presents some disadvantages, including false-positive results due to pneumococcal colonization, particularly among children, and long-lasting positive results after antibody treatment (32,33). Therefore, other detection methods for rapidly identifying pneumococcal pneumonia have been developed by several laboratories.…”