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HelpTest Code TSH RFLX FT4 TSH, Reflex to Free T4
Additional Codes
LAB13042
Performing Laboratory
Central Peninsula Hospital
Collection Method
Venipuncture
Container
Gold Top SST
Specimen Type
Preferred
- Serum- Gold Top SST or Red Top
Acceptable
- Plasma- Light Green Top (Lithium heparin)
Minimum Volume
0.5ml
Specimen Stability
| Ambient | 8 days |
| Refrigerated (4°C to 8°C) | 14 days |
| Frozen(-40°C to 0°C) | 2 years |
Reference or Target Ranges
| Age | Male | Female |
| < 1 month | Reference Range Not Established | Reference Range Not Established |
| 1 month to 18 years | 0.5 - 6.0 | 0.5 - 6.0 |
| > 18 years | 0.27 - 4.20 | 0.27 - 4.20 |
Reportable Units
uIU/mL
Critical Value
Not defined for this assay
Reasons for Rejection
| Hemolysis Threshold | 1000 mg/dL |
| Icterus Threshold | 41 mg/dL |
| Lipemia Threshold | 1500 mg/dL |
| Other | QNS, contaminated, improperly Labeled, improper specimen type |
Performance Information
| Days and Time Performed | 24/7 |
| Expected Turn Around Time |
Stat: 1 hour Routine: 4 hours |
| Stat Availability | Yes |
| Performing Bench | CPH Chemistry |
| Methodology/Method Description | Roche Cobas |
Reflex Testing
TSH will reflex to FT4 if result is:
<0.270 or >4.200
CPT Codes
TSH, Reflex to Free T4 - 84443
T4 (Thyroxine), Free, Serum - 84439
Last review/edit date
2025