Table 2.
Characteristics of TREC assay and screening algorithm of cohort studies included in systematic review
| Borte et al. [13] | Adams et al. [16] | Audrain et al. [12] | Chien et al. [26] |
Verbsky et al. [25] Wisconsin |
Kwan et al. [34] California |
Vogel et al. [33] New York State |
||
| TREC assay characteristics | ||||||||
| Punch size | 3.2 mm ~3 μl blood | 1.5mma | 3.2 mm | 3.2 mm | 3.2 mm | 3.2 mm | 3 mm | |
| DNA elution/extraction method | Generation DNA elution solution QIAGEN | DNA elution | Washing & elution with S2 | Generation DNA elution solution QIAGEN |
Generation DNA purification solution and Generation DNA elution solution QIAGEN |
DNA elution Generation DNA purification and elution solution QIAGEN |
Wash/red cell lysis buffer | |
| Platform quantitative PCRb | RT-qPCR | PCR – probe hybridization – Victor EnLite fluorometer | RT-qPCR | RT-qPCR | RT-qPCR |
RT-qPCR (Light cycler) |
RT-qPCR | |
| PCR set-up | Triplex RQ-PCR: TREC/KREC/ACTB | TREC single plex | TREC/RNAseP multiplex | TREC singleplex | TREC single plex | TREC single plex | TREC single plex | |
| Control gene | ACTB (β-actin) | ACTB (β-actin) | RNAseP | RNAseP | ACTB (β-actin) | ACTB (β-actin) | RNaseP | |
| TREC cut-off value | 15 TRECs/μl | 15 TRECs/μl | 100 (183) TRECs/μl | 40 TRECs/μl | 25 / 40 TRECs/μl | 40TRECs/μl (25 TRECs/μl) in repeat test | 125 (200) TRECs/μl | |
| Positive control | Plasmid | Calibrator samples (consisted of three DBS calibrators, A-C, with known quantities of TREC and ß-actin DNA) | Plasmid | NR | Plasmid | Plasmid | Plasmid | |
| Algorithm | ||||||||
| Initial TREC measurement without control gene | − | + | − | − | + | + | − | |
| Re-testing new punch initial Guthrie card | + | + | + | − | + | + | + | |
| Borderline category | − | − | + | − | − | − | + | |
| Repeat DBS in case of insufficient control gene amplification | + | + | + | NR | + | + | NR | |
| Repeat DBS in borderline category | NA | NA | NR | NA | NA | NA | + | |
| Repeat DBS at 37weeks gestational age for premature with abnormal screen | − | − | − | − | + | − | + | |
| Repeat DBS for NICU patients with abnormal screen | − | − | − | − | − | + | − | |
| Immediate referral when low TREC and normal control upon singulate initial testing | − | NA | NR | + | NA | NA | + | |
|
Kwan et al. [36] Colorado |
Kwan et al. [36] Connecticut |
Kwan et al. [36] Delaware |
Kwan et al. [36] Massachusettsf |
Kwan et al. [36] Michigan |
Kwan et al. [36] Mississippi |
Kwan et al. [36] Navajo Nation |
Kwan et al. [36] Texas |
|
| TREC assay characteristics | ||||||||
| Punch size | NR | NR | NR | 3.2 mm | NR | 3.2 mm | 3.2 mm | NR |
| DNA elution/extraction method | NR | NR | NR | Washing & elution with S2 | NR |
DNA elution Generation DNA purification and elution solution QIAGEN |
DNA elution Generation DNA purification and elution solution QIAGEN |
NR |
| Platform quantitative PCRb | NR | NR | NR | RT-qPCR | NR | RT-qPCR (Light cycler) | RT-qPCR (Light cycler) | NR |
| PCR set-up | NR | NR | NR | TREC/RNAseP multiplex | NR | TREC single plex | TREC single plex | NR |
| Control gene | ACTB (β-actin) | RNaseP | RNaseP | RPaseP | ACTB (β-actin) | ACTB (β-actin) | ACTB (β-actin) | RNaseP |
| TREC cut-off value | 40 TRECs/μl | 30/25 TRECs/μlc | 16 (26) TRECs/μl | 252 TRECs/μl | 7 (11) TRECs/μl | 40TRECs/μl (25 TRECs/μl) in repeat test | 40TRECs/μl (25 TRECs/μl) in repeat test | 150 (200)/110c |
| Positive control | NR | NR | NR | Plasmid | NR | Plasmid | Plasmid | NR |
| Algorithm | ||||||||
| Initial TREC measurement without control gene | + | − | − | − | − | + | + | + |
| Re-testing new punch initial Guthrie card | + | + | NR | + | − | + | + | + |
| Borderline category | − | + | + | − | + | − | − | + |
| Repeat DBS in case of insufficient control gene amplification | + | + | + | + | + | + | + | + |
| Repeat DBS in borderline category | NA | + | NR | NA | + | NA | NA | + |
| Repeat DBS at 37weeks gestational age for premature with abnormal screen | − | − | +d | − | − | − | − | − |
| Repeat DBS for NICU patients with abnormal screen | − | − | − | − | − | + | + | − |
| Immediate referral when low TREC and normal control upon singulate initial testing | NA | + (if <10 TRECs/μl and control gene cycle threshold <28) | NRe | − | + | NA | NA | − |
+ algorithm did involve item, − algorithm did not involve item, NA not applicable, NR not reported
aEnLite neotatal TREC kit (Perkin Elmer)
bRT-qPCR refers to TaqMan technology (Applied Biosystem)
cLower cut-off for preterm infants
dDBS repeated at 38 weeks
eNo cycle threshold – 3 TRECs: Alert, handling NR