1 thyroid testing strategies in the south-west and wessex a survey conducted on behalf of the acb...
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Thyroid Testing Strategies in the South-West and Wessex
A survey conducted on behalf of the ACB SW&W Regional Committee by
Roberta Goodall
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Survey Structure and Responses
• Questionnaire e-mailed to audit leads • 24 laboratories surveyed
– 13 South West, 11 Wessex– 2 known 'pairs' (ie shared protocol/testing)– 1 assumed pair– 21 expected responses
• 20 questionnaires returned
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Test SW labs Wessex labs Total
TSH only 9 5 14
TSH + fT4 1 4 5
TSH + fT3 1 1
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Q1. What is (are) your frontline test(s) for thyroid function?
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Q2. What are your reference ranges?
Nearly all different – even with same instrument
Ranges below show lowest quoted lower limits with highest upper limits
TSH mU/L fT4 pmol/L fT3 pmol/L
0.03 – 6.9 7 – 26 to 7.8*
Smallest 0.27 – 4.2 10 – 20 4.0 – 6.8 (2.5-5.3)
Largest 0.3 – 6.0 7 – 26 3.2 – 7.8
* One lab goes as high as 8.8 on an age related range (<40yrs)
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Q3. Do you perform reflex testing?
'No'
TSH+fT4 3/5
'Yes'
TSH only 14/14
TSH+fT4 2/5
TSH+fT3 1/1
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Q3. What is/are the rule(s) and the reflex analyte(s)?
Based on front–line result
TSH TSH/fT4 TSH/fT3
TSH low – add fT4 9TSH low – add fT3 5 1TSH high – add fT4 10fT4 high – add fT3 1Low TSH, on T4 – add fT4 2Persistent elevated TSH – add TPO 1
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Q3. What is/are the rule(s) and the reflex analyte(s)?
• Frontline can change based on certain criteria, for example• Paediatric patients always get both – 7/20 respondents• Certain consultants get fT4 frontline (or whatever they ask for) –
1(2)/20
• Clinical information will change request – 2nd line rather than reflex? – too many to list but e.g
• Differentiation made between diagnostic testing (TSH only) and known disease
• fT4 added to both treated hypos and hypers• fT4 (and fT3) added to hypopit
• Concomitant therapy eg amiodarone, Li, get fT4 (and fT3) regardless• All rules / protocols can change at the discretion of the signer at
clinical validation.
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Q3. How is it / are they activated?
17 / 20 perform (rule based?) reflex testing
Automatically by computer/analyser 4
At technical validation by BMS 1
At clinical authorisation 3
Basic rule auto / extras at validation 8
Basic rule at TA / extras at validation 1
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Q3. What proportion cascade to a second line test?
0 – 10% 7 (4 were < 5%)
11 – 20% 5
21 – 30% 2
31 – 40% 1
41 – 50% 0
51 – 60 % 1
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Q4. Do you have criteria for requesting / analysing thyroid antibodies and, if so, what are they and
which antibodies do you perform / request?
No criteria (or other explanation) 3
Done elsewhere (no other information given) 1
TPO antibody 11
Anti-T4 1
TSH receptor antibodies 1
Type not stated (assume TPO) 3
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Criteria for TPO (14/16)(recommended, suggested, requested)
TSH TSH/fT4 TSH/fT3
Borderline / slight TSH (usually on rpt) 3 2 1
TSH (persistent/gross, discretion of signer) 1
Not defined (discretion of signer) 2
Rarely / not suggested 1
Suspicious/mismatched results 1
Sub-clinical / compensated hypo 2 1
Q4. Do you have criteria for requesting / analysing thyroid antibodies and, if so, what are they and
which antibodies do you perform / request?
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Q5. What analytical platform do you use for your thyroid function tests?
TSH TSH/fT4 TSH/fT3
Roche Elecsys 1 1
Bayer Centaur 4 3
DPC Immulite 3 1
Roche Modular 3
Beckman Access + IMX 1
Abbott AxSym 1
Immuno 1 2
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Q6. What is your annual TFT workload?
Number of TFT requests (1000s pa)
TSH TSH/fT4 TSH/fT3
20 – 30 2
30 – 40 1 1
40 – 50 5 1
50 – 60 1
60 – 70 4 1
70 – 80 1
80 – 90 1
90 – 100 1 1
100 – 110 1
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Q7. - any comments?
• ' ….remain unconvinced of the need to go over to dual
frontline. This would cost an additional £60K/year, plus the
need for another analyser. fT4 is also more of a problem
assay and if always done could lead to more patients being
investigated for possible hypopit at considerable extra cost.'
• ' ? dual front-line vs TSH only must be a quality, not a cost
issue'
• ' we have always performed fT4 and TSH frontline. We pick
up approx 6-8 hypopit pts/year (38,000 requests pa) that
would otherwise be missed using TSH alone'
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• 'Not averse to frontline TSH. Would however miss some
hypopit. + miss other relevant findings eg if anti-thyroid
drug therapy not recorded
• 'We wish to introduce frontline fT4 plus TSH (in line
with current guidelines) but have not had success getting
funding although we are supported by our
endocrinologist.
• 'The reasons for not having dual front line TSH and fT4
on all samples are largely economic.'
Q7. - any comments?