BD ProbeTec Manual Del Usario página 12

EXPECTED RESULTS
NOTE: An explanation of symbols and abbreviations used in tables can be found in the Interpretation of Tables section
(at end of insert).
A. Prevalence
The prevalence of positive C. trachomatis specimens in patient populations depends upon: clinic type, age, risk factors,
gender, and test method. The prevalence observed with the CT Q
from 8.5% to 18.3% for female specimens and 0% to 24.1% for male specimens (Table 9).
B. Positive and Negative Predictive Value
Hypothetical positive and negative predictive values (PPV & NPV) for the CT Q
calculations are based on hypothetical prevalence and overall sensitivity and specificity (compared to the patient
infected status) of 94.5% and 98.9%, respectively. In addition, PPV and NPV based on actual prevalence, sensitivity
and specificity are shown in Tables 8 and 9. PPV was calculated using: (Sensitivity x Prevalence) / (Sensitivity x
Prevalence + [1 - Specificity] x [1 - Prevalence]). NPV was calculated using: (Specificity x [1 - Prevalence]) / ([1-Sensitivity]
x Prevalence + Specificity x [1-Prevalence]).
C. MaxRFU Frequency Distribution
A total of 5388 CT Q x Assay results was evaluated at seven geographically diverse clinical sites. A frequency
distribution of the initial MaxRFU values for the CT Q
x
from CT Q true positive, true negative, false positive and false negative specimens (i.e., from those specimens that
yielded results which were discordant with the patient infected status [PIS]) is shown in Table 6.
Figure A: Frequency Distribution of MaxRFU for the CT Q
Table 5: CT Hypothetical Positive and Negative Predictive Values Compared
to Patient Infected Status.
Prevalence Sensitivity
(%) (%)
2 94.5
5 94.5
10 94.5
20 94.5
30 94.5
40 94.5
50 94.5
x Assay during a multi-center clinical trial ranged
Specificity PPV
(%) (%)
98.9 64.1
98.9 82.1
98.9 90.7
98.9 95.6
98.9 97.4
98.9 98.3
98.9 98.9
x assay is shown in Figure A. The distribution of MaxRFU values
x Assay
11
x Assay are shown in Table 5. These
NPV
(%)
99.9
99.7
99.4
98.6
97.7
96.4
94.7