Background
Screening tool | HCV-Ab | HCV-Ag | PCR for HCV RNA |
---|---|---|---|
Benefits | ♦ Widely available; ♦ Inexpensive; ♦ Much experience and data for use as first-line approach to screening for HCV exposure (underpins many old seroprevalence studies). | ♦ Diagnostic of active infection (not past exposure); | ♦ Accepted gold-standard diagnostic test for active infection (not past exposure); ♦ Allows quantitative monitoring of viraemia; useful for monitoring therapy; ♦ Genome amplification allows other information to be ascertained (e.g. genotype; drug resistance); ♦ Can potentially be applied to dried blood spots (DBS). |
Challenges | ♦ Subject to inter-assay variability and a variable rate of false positive results [46, 47]; false positive has been associated with ethnicity [48, 49], age [48], raised IgM and erythrocyte sedimentation rate (ESR) [46], auto-antibodies [50], and prosthetic devices [51]; ♦ Test of exposure, not of active infection, so should be followed up with a more specific diagnostic test. | ♦ Not universally available; ♦ More expensive than HCV-Ab; ♦ Not consistently regarded as sufficiently sensitive to replace PCR. | ♦ Not universally available; ♦ Expensive: beyond the financial reach of many resource-limited settings. |
Methods
Setting and cohort
Data analysis
Ethics approval
Results
HCV testing: Frequency and characteristics of infection
Group 1 (2014) | Group 2 (2016) | Group 1 + Group 2 (2014–2016) | |
---|---|---|---|
Total number HCV-Ab positive | 317 | 325 | 642 |
Total number confirmed positive for active HCV infection (HCV-Ag/HCV RNA positive) | 191 | 162 | 353 |
Number male (% of active infections)a,b | 165 (86.3%) | 132 (81.5%) | 297 (84.1%) |
Age in years (median and IQR)a | 39 (31–49) | 36 (30–46) | 37 (31–48) |
Locationa, c | |||
- Primary Care | 64 (33.5%) | 46 (28.4%) | 110 (31.2%) |
- Hospital out-patient | 17 (8.9%) | 17 (5.2%) | 34 (9.6%) |
- Prison | 61 (31.9%) | 66 (40.7%) | 127 (35.9%) |
- Hospital in-patientd | 22 (11.5%) | 9 (5.5%) | 31 (8.8%) |
- Emergency Dept. | 5 (2.6%) | 6 (3.7%) | 11 (3.1%) |
- Sexual health clinic | 16 (8.4%) | 13 (8.0%) | 29 (8.2%) |
- Occupational health | 2 (1.0%) | 1 (0.6%) | 3 (0.8%) |
- Other locationse | 4 (2.1%) | 4 (2.5%) | 8 (2.3%) |
Ethnic origina | |||
- Black | 5 (2.6%) | 1 (0.6%) | 6 (1.7%) |
- Asian | 17 (8.9%) | 7 (4.3%) | 24 (6.8%) |
- European | 149 (78.0%) | 100 (61.7%) | 249 (70.5%) |
- Unknown | 20 (10.5%) | 54 (33.3%) | 74 (21.0%) |
Outcomes and performance of HCV-ab and HCV-ag assays
Outcome | Result (n)* |
True positive | 121 |
False negative | 7 |
False positive | 0 |
True negative | 67 |
Test characteristic | Result (%) |
Sensitivity | 94.5 |
Specificity | 100 |
Positive predictive value | 100 |
Negative predictive value | 90.5 |
Age group (years) | Sex | Patient location | Ethnicity | HIV status | HCV Ag (fmol/L) | HCV Ab (sample/cut-off ratio) | Genotype | HCV viral load (IU/ml) |
---|---|---|---|---|---|---|---|---|
30–39 | F | Sexual health | Unknown | negative | 0.0 | 11.8 | N/A | 25 |
40–49 | M | Primary care | European | negative | 0.0 | 12.2 | N/A | 226 |
50–59 | F | Hospital in-patient (General Medicine) | European | positive | 0.0 | 3.1 | N/A | 302 |
20–29 | M | Prison | European | negative | 0.62 | 14.2 | 2b | 2916 |
20–29 | M | Prison | European | N/A | 0.00 | 12.6 | N/A | 8232 |
30–39 | F | Hospital out-patient | European | N/A | 1.98 | 15.8 | 1b | 13,860 |
30–39 | M | Prison | European | negative | 0.00 | 12.2 | 3a | 174,834 |
Clinical management and outcomes
Discussion
Summary comments
Treatment Status | Patient Classification | Number | Percentage of treatment subgroupa | Percentage of total cohort |
Not yet treated (n = 130) | Offered appointment but did not attend | 46 | 35.4 | 13.0 |
Seen in another clinic (sexual health, prison, paediatrics) | 32 | 24.6 | 9.1 | |
Seen by hepatology but not on treatment waiting list | 23 | 17.7 | 6.5 | |
Seen by hepatology and on treatment waiting list for DAA | 3 | 2.3 | 0.9 | |
Died | 11 | 8.5 | 3.1 | |
Transferred out of area | 10 | 7.7 | 2.8 | |
Seen in clinic but lost to follow-up | 2 | 1.5 | 0.6 | |
Spontaneous clearer | 3 | 2.3 | 0.8 | |
Treated with DAA (n = 59) | SVR12 | 50 | 84.7 | 14.2 |
Relapsed | 4 | 6.8 | 1.1 | |
Outcome data pending | 5 | 8.5 | 1.4 | |
Treated with IFN/RBV (n = 20) | SVR12 | 16 | 80.0 | 4.5 |
Relapsed | 3 | 15.0 | 0.8 | |
No outcome data | 1 | 5.0 | 0.3 | |
Unknown (n = 150) | Not known to local services | 144 | 100 | 40.8 |
TOTAL | 353 | 400 | 100 |