Table 2.
Proportion of Positive Findings on Quantitative Reverse-Transcriptase–Polymerase-Chain-Reaction (RT-PCR) Assay and Cycle-Threshold Values in the Semen of Survivors of EVD, According to Time after ETU Discharge.
| Time after ETU Discharge | Phase 1 | Phase 2 | ||||
|---|---|---|---|---|---|---|
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|
|
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| Positive Result | Cycle-Threshold Value* | Positive Result | Cycle-Threshold Value† | |||
| NP target | VP40 target | NP target | GP target | |||
| no./total no. (%) | median (range) | no./total no. (%) | median (range) | |||
| 0–3 Mo | 7/7 (100) | 32.4 (20.9–36.0) | 31.3 (20.2–34.9) | — | — | — |
|
| ||||||
| 4–6 Mo | 25/39 (64) | 34.3 (26.3–38.6) | 33.1 (26.1–39.7) | 1/3 (33) | 35.8 | 34.8 |
|
| ||||||
| 7–9 Mo | 13/48 (28) | 37.4 (28.5–38.8) | 36.6 (28.2–38.3) | 2/12 (17) | 35.0–35.1 | 32.9–34.4 |
|
| ||||||
| 10–12 Mo | 1/4 (25) | 37.7 | 36.9 | 3/22 (14) | 38.0‡ | 37.1 (36.0–37.5) |
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| 13–15 Mo | — | — | — | 4/38 (11) | 35.3 (32.7–37.4) | 34.4 (31.1–36.7) |
|
| ||||||
| 16–18 Mo | — | — | — | 1/25 (4) | 37.9 | 37.7 |
|
| ||||||
| ≥19 Mo | — | — | — | 0/12 | — | — |
Cycle-threshold values were assessed in participants who had positive results; if only one participant had a positive result, that value is shown. The value was determined by means of the assay from the Centers for Disease Control and Prevention, which was a quantitative RT-PCR assay that used Ebola virus–specific gene targets (NP and VP40) and the human β2-microglobulin (B2M) gene, as described previously.19–21 The findings were considered to be positive if the VP40 and the NP gene targets were both detected within 40 cycles of replication. Higher cycle-threshold values indicate lower RNA levels. The findings were considered to be negative if both Ebola virus gene targets were not detected and the findings regarding B2M status were positive. The findings were ruled to be indeterminate if one of the VP40 or NP gene targets was detected but not both. The results for one participant from whom a specimen was obtained at 10 months were indeterminate.
Cycle-threshold values were assessed in participants who had positive results. For phase 2, the median of the cycle-threshold value is not presented if data were available for fewer than three participants; in that case, the range is presented if there were two observations, and a single value is presented when there was just one observation. The value was determined by means of the assay from the Chinese Center for Disease Control and Prevention, which was a double-channel quantitative RT-PCR detection kit that used Ebola virus NP and GP and B2M.22 The findings were considered to be positive if either the NP or GP gene target was detected within 38 cycles of replication. The findings were considered to be negative if both Ebola virus gene targets were not detected and the findings regarding B2M status were positive.
A cycle-threshold value of 38.0 indicates a negative result. A single value is reported here because values were missing for the other two participants.