Product Manual

Page 10 of 15
Sofia Strep A FIA
LIMITATIONS
 The contents of this kit are to be used for the qualitative detection of Group A Streptococcal antigens from throat Swab
specimens.
 The test detects both viable and nonviable Group A Streptococcus bacteria and may yield a positive result in the
absence of living organisms.
 Respiratory infections, including pharyngitis, can be caused by Streptococcus from serogroups other than Group A, as
well as other pathogens.
 The Sofia Strep A FIA will not differentiate asymptomatic carriers of Group A Streptococcus from those exhibiting
Streptococcal infection.
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 A negative test result may occur if the level of antigen in a sample is below the detection limit of the test or if the sample
was collected, transported, or stored improperly.
 Failure to follow the Test Procedure may adversely affect test performance and/or invalidate the test result.
 Patients with symptoms and an antigen negative test should have a follow-up culture.
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 Test results must be evaluated in conjunction with other clinical data available to the physician.
 Negative test results do not rule out possible other infections.
 Positive test results do not rule out co-infections with other pathogens.
EXPECTED VALUES
Group A Streptococcus bacteria are responsible for about 19% of all upper respiratory tract infections.
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Infection is most
prevalent in winter and early spring, with most cases arising in patients living in highly populated areas. Consistent with
these figures, in the multi-center clinical study conducted by Quidel during 2011 and 2012, 17.4% (128/736) of the patients
presenting with pharyngitis were found to be culture positive for Strep A. Nearly half of these subjects, 46%, were male.
The subjects’ ages ranged from 3-72 years and 88% (647/736) were children (3-17 years of age).
PERFORMANCE CHARACTERISTICS
Sofia Strep A FIA Performance vs. Cell Culture
The performance of the Sofia Strep A FIA was compared to standard bacterial culture and identification in a multi-center
clinical field study. This study was conducted by health care personnel during 2011 and 2012 at eight (8) distinct sites in
various geographical regions within the United States and two (2) sites in Australia. In this multi-center, point-of-care (POC)
field trial, two (2) throat Swabs were collected from 736 patients with symptoms suggestive of bacterial pharyngitis.
One (1) throat Swab was transported on cold ice packs to a central Reference Laboratory, streaked on a sheep blood
agar plate (SBA) and cultured for up to 48 hours. Immediately after streaking, this same Swab was tested in the rapid
Sofia Strep A FIA. The performance of the Sofia Strep A FIA was determined by comparison of the rapid test result to the
corresponding culture result. The results from these analyses are presented in Tables 2, 3a, and 3b.
Table 2
Sofia Strep A FIA Results: Combined
Culture Sens. = 90.6% (116/128)
Pos Neg Total:
(95% CI: 84.3%-94.6%)
Sofia Pos 116 24 140 Spec. = 96.1% (584/608)
Sofia Neg 12 584 596
(95% CI: 94.2%-97.3%)
Total: 128 608 736 PPV = 82.9% (116/140)
NPV = 98.0% (584/596)
Prev. = 17.4% (128/736)