Spectrum and Inoculum Size Effect of a Rapid Antigen Detection Test for Group A Streptococcus in Children with Pharyngitis
Advanced Search
Select up to three search categories and corresponding keywords using the fields to the right. Refer to the Help section for more detailed instructions.

Search our Collections & Repository

For very narrow results

When looking for a specific result

Best used for discovery & interchangable words

Recommended to be used in conjunction with other fields

Dates

to

Document Data
Library
People
Clear All
Clear All

For additional assistance using the Custom Query please check out our Help Page

i

Spectrum and Inoculum Size Effect of a Rapid Antigen Detection Test for Group A Streptococcus in Children with Pharyngitis

Filetype[PDF-95.73 KB]


English

Details:

  • Alternative Title:
    PLoS One
  • Personal Author:
  • Description:
    Background

    The stability of the accuracy of a diagnostic test is critical to whether clinicians can rely on its result. We aimed to assess whether the performance of a rapid antigen detection test (RADT) for group A streptococcus (GAS) is affected by the clinical spectrum and/or bacterial inoculum size.

    Methods

    Throat swabs were collected from 785 children with pharyngitis in an office-based, prospective, multicenter study (2009–2010). We analysed the effect of clinical spectrum (i.e., the McIsaac score and its components) and inoculum size (light or heavy GAS growth) on the accuracy (sensitivity, specificity, likelihood ratios and predictive values) of a RADT, with laboratory throat culture as the reference test. We also evaluated the accuracy of a McIsaac-score–based decision rule.

    Results

    GAS prevalence was 36% (95CI: 33%–40%). The inoculum was heavy for 85% of cases (81%–89%). We found a significant spectrum effect on sensitivity, specificity, likelihood ratios and positive predictive value (p<0.05) but not negative predictive value, which was stable at about 92%. RADT sensitivity was greater for children with heavy than light inoculum (95% vs. 40%, p<0.001). After stratification by inoculum size, the spectrum effect on RADT sensitivity was significant only in patients with light inoculum, on univariate and multivariate analysis. The McIsaac-score–based decision rule had 99% (97%–100%) sensitivity and 52% (48%–57%) specificity.

    Conclusions

    Variations in RADT sensitivity only occur in patients with light inocula. Because the spectrum effect does not affect the negative predictive value of the test, clinicians who want to rule out GAS can rely on negative RADT results regardless of clinical features if they accept that about 10% of children with negative RADT results will have a positive throat culture. However, such a policy is more acceptable in populations with very low incidence of complications of GAS infection.

  • Subjects:
  • Source:
  • Document Type:
  • Place as Subject:
  • Volume:
    7
  • Issue:
    6
  • Collection(s):
  • Main Document Checksum:
  • Download URL:
  • File Type:

You May Also Like

Checkout today's featured content at stacks.cdc.gov