Purpose The objectives of the present study were to evaluate whether investigator bias influenced the Convergence Insufficiency Symptom Survey (CISS) scores of children with normal binocular vision (NBV) in our original validation study, reevaluate the usefulness of the cut-off score of 16, and reexamine the validity of the CISS. Methods Six clinical sites participating in the Convergence Insufficiency Treatment Trial (CITT) enrolled 46 children 9 - <18 years with NBV. Examiners masked to the child’s binocular vision status administered the CISS. The mean CISS score was compared to that from the children with NBV in the original, unmasked CISS study and also to that of the 221 symptomatic CI children enrolled in the CITT. Results The mean (±SD) CISS score for 46 subjects with NBV was 10.4 (±8.1). This was comparable to that from our prior unmasked NBV study (mean = 8.1(± 6.2); p = 0.11), but was significantly different from that of the CITT CI group (mean = 29.8 ± 9.0; p < 0.001). Eighty-three percent of these NBV subjects scored less than 16 on the CISS, which is not statistically different from the 87.5% found in the original unmasked study (p = 0.49). Conclusions Examiner bias did not affect the CISS scores for subjects with NBV in our prior study. The CISS continues to be a valid instrument for quantifying symptoms in 9 to <18 year-old children and these results confirm the validity of a cut-point of ≥ 16 in distinguishing children with symptomatic CI from those with NBV.

The results presented in this report demonstrate that the sequential use of screening immunoassays before immunoblot testing can significantly reduce both the number of immunoblot tests and proportion of indeterminate results, without impacting sensitivity, thereby improving algorithm efficiency and simplifying donor management.

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Our analysis suggests that a combination of indicators can be used to help clarify RIBA-3-indeterminate, RNA-negative results. Specifically, donors with high S/CO ratios on a screening immunoassay, RIBA-3 reactivity to c22p or c33c with band intensity of 2+ or greater, without a previous history of negative or BFR donations and with an identifiable risk factor, have a high probability of representing true anti-HCV rather than nonspecific reactivity.

Although high s/co ratios were predictive of confirmed-positive results in all four assays, a number of confirmed-positive samples gave low values while some biologic false-positive samples showed high values. As the s/co ratio distributions for BFR and confirmed-positive results overlapped for all four PRISM assays, this study highlights the importance of serologic confirmatory testing and the need for caution when using screening IA results to assign a final donor status.