Performance of the ready-made filovirus test kit. A, Testing of plaque-quantified virus stock solutions. Virus was diluted in virus-negative human serum to the listed concentrations and tested in 4 replicate assays each. +, positive result; − negative result; RT-PCR, reverse-transcription polymerase chain reaction. B, Probit analysis on replicated tests (typically 6 tests per concentration) of virus-negative human serum inoculated on the level of the lysis buffer with given concentrations (X-axis) of filovirus RNA in vitro transcripts. The observed rates of positive results per total no. of tests performed are plotted on the Y-axis. Nos. in each panel are the concentrations beyond which the statistical chance of detection exceeds 95%, according to the probit model (dose-response relationship). Nos. in parenthesis are 95% confidence intervals for these numbers. cps, copies.