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Tg + Recovery: reliable strategies to overcome assayinterferences and to increase applicable Tg results
of thyroid cancer patientsconfident follow-up
Thermo Scientific B·R·A·H·M·S TgImmunodiagnostic Assays
undisturbed measurement
disturbed measurement (I)
disturbed measurement (II)
Tg
I125
Tg
I125
Tg
Thyroglobulin (Tg) is a highly specific tumor markerfor differentiated thyroid carcinoma. Its measurementin serum represents one of the most efficient toolsfor early detection of tumor relapse after an effectiveprimary therapy.
Interferences, particularly by anti-Tg autoanti bodies,often give rise to false Tg results. This might occur,even with newly developed Tg assays, in spite of their improve ments that have been made by themanufacturers.
This problem appears to be quite a challenge forlaboratory practice. We will try to approach thisphenomenon with the help of examples and will showand validate ways to resolve this problem.
Anti-Tg autoantibodies causing interferences
Anti-Tg autoantibody not causing interferences
1st assay antibody
2nd assay antibody
Thyroglobulin in serumTg
Assay interferences
• Real Tg level: 5 ng/mL
• Tg antibodies causing interferences: 1000 U/mL
• Measured Tg level: 0 ng/mLPatient Bwith anti-Tgantibodies causinginterferences
• Real Tg level: 5 ng/mL
• Tg antibodies causing interferences below detection limit
• Measured Tg level: 0 ng/mLPatient Cwith not detectableanti-Tg antibodiescausinginterferences
Tg result will be discarded!
Tg result will be discarded!
• Real Tg level: 5 ng/mL
• Tg antibodies not causing interferences: 1000 U/mL
• Measured Tg level: 5 ng/mL
Tg
I125
Tg result will be falsely considered valid!
Patient Awith anti-Tgantibodies not causinginterferences
Tg antibody measurement
Tg
I125
Tg
+50 ng/mL Recovery Tg
Patient’s sampleMeasured Tg level:0 ng/mL
Recovery sampleMeasured Tg level:28 ng/mL
5ng/mLTg
+50 ng/mL Recovery Tg
Patient’s sampleMeasured Tg level:0 ng/mL
Recovery sampleMeasured Tg level:28 ng/mL
5ng/mLTg
Tg result is considered valid!
Tg result will be discarded!
Tg result will be discarded!
• Real Tg level: 5 ng/mL
Recovery
+50 ng/mL Recovery Tg
>55 ng/mL– 5 ng/mL 50
50 ng/mL 50 Patient’s sampleMeasured Tg level:5 ng/mL
Recovery sampleMeasured Tg level:55 ng/mL
= 100%=
Recovery
>28 ng/mL– 0 ng/mL 28
50 ng/mL 50 = 56%=
Recovery
>28 ng/mL– 0 ng/mL 28
50 ng/mL 50 = 56%=
5ng/mLTg
5ng/mLTg
5ng/mLTg
5ng/mLTg
• Real Tg level: 5 ng/mL
• Tg antibodies causing interferences: 1000 U/mL
• Real Tg level: 5 ng/mL
• Tg antibodies causing interferences below detection limit
Tg recovery test
...and how to overcome
The validation of a measured serum Tg result by deter -mining only anti-Tg autoantibodies involves the risks:
• not to consider accurate Tg results (see Patient A)• not to recognize invalid falsely low Tg levels assuch and to consider them as valid (see Patient C)
The measurement of Tg recovery guarantees the mostefficient and effective classification of “valid”and“invalid” Tg results.
The rate of applicable Tg results increases.
105367.4
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Clinical Diagnostics
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B·R·A·H·M·S Tg-pluS RIA
B·R·A·H·M·S Tg-pluS LIA
B·R·A·H·M·S Tg-S RIA
B·R·A·H·M·S Tg-S Recovery RIA
B·R·A·H·M·S hTg KRYPTOR (with Recovery)
B·R·A·H·M·S anti-Tg RIA
B·R·A·H·M·S anti-Tgn RIA
B·R·A·H·M·S anti-Tgn LIA
B·R·A·H·M·S anti-Tgn KRYPTOR
Thermo Scientific B·R·A·H·M·S Tg and anti-Tg assays
