Quality and uncertainty in screening assays from taking the sample to issuing the result Prof Jim Bonham Laboratory lead PHE Screening
Outline Ensuring that the testing operates smoothly as a programme not just a test Sample quality Assay quality and population monitoring Sample transport Reporting results and confirmatory testing
The quality of the spot xLeu: The edge of a large spot vs the centre of a small spot, approx 35% difference at 400 µmol/L ie 10 µL 20 µL 50 µL 75 µL +/- 70 µmol/L K Hall : 2014, personnel Communication
Blood Spot Quality
Blood spot quality Baby X Card 1 Front Back • Date of Birth 17/10/15 • Date of Specimen 22/10/15 (Day 5) • Received in laboratory 23/10/2015 (Friday) and processed. • Results reviewed on 26/10/2015 (Monday). • Poor quality spot (probably spot 1). • Result: C8= 0.39 Near Miss: A False Negative MCAD Screening Test Due To A Poor Quality Blood Spot
Blood spot quality Baby X Card 2 Front Back • An urgent repeat sample was requested by phone. • Received and analysed 26/10/15. • Results: C8= 0.66 C10= 0.3 C8:C10 = 2.2 • Referral was made 18:49 26/10/15. Baby was seen on the 27/10/2015. • Near Miss: A False Negative MCAD Screening Test Due To A Poor Quality Blood Spot
Method performance EQA experience • Leu (n=273), mean 168 µmol/L UL(95%) 231, LL (95%) 104 • C5 (n=268), mean 2.0 µmol/L UL(95%) 2.7, LL (95%) 1.4 • Met (n=261), mean 21 µmol/L UL(95%) 28, LL (95%) 13 • C5DC (n=275), mean 2.1 µmol/L UL(95%) 3.7, LL (95%) 0.40 CDC QAP Q3 2014
What have we done – population monitoring? • Each lab submits data and receives monthly and quarterly report • Reports are summarised by analyte • Snapshot of how one lab compares to another • Box whisker plots - scaled to analytical cut-off value Gives 10 th , 50 th , 90 th and 99 th centiles for each lab relative to “all • labs” data • Results split by instrument for each lab • Useful for identifying any significant bias • Regular meetings to discuss performance
What do we find - assay quality Xle - Feb 2016 C5 - Feb 2016 500 1 450 0.9 400 0.8 350 0.7 µmol/L 300 0.6 µmol/L 250 0.5 200 0.4 150 0.3 100 0.2 50 0.1 0 0 B B C C G G L L L M N O O P P S S V V A a e e i h B B C L L L M N O O S V V i r i r a v e x x o o t i i l C G G P P S A O O e e a a a e e i m m r e f f e l i i a a o o h t i i m w r r H p p r r O O v e x x l d S S d d n o o L r e e a e a a l r t t f m m m e w f f H H H c c s s f e a a a d n r r p p i i b i s s p r r S S d d o o t t f L n n f m m i r f h a d d e l t t b H H c c s s f e a a a r 1 2 o i h h i i b i f s s p r r i g g i 1 2 s e s n n h a d d m m l t t b 1 o e 1 2 l r f e i h h d t o o d 1 2 o h h s r 1 2 g g i 1 2 e s l e s g l l u u 1 o 1 2 a a t h h d t o o d r e 1 1 s 1 2 e 1 e t t g l l u u m m a a t e 1 h h 1 1 r e 1 e 2 m m t t 1 h h 1 2 1 1 2 r 2 1 2 1 1 2 Met - Feb 2016 45 40 35 30 µmol/L 25 20 15 10 5 0 B B C C G G L L L M N O O P P S S V V A a e e i h i i a v e x x o o t i i l r r O O a a a r e e e l m m m e w f f r r H p p d d d n o o L S S r t t f e a i i b i H H s s p c c r r s s f a a n n f i h a d d m m e l t t b r f o i g g 1 2 1 2 e h h i 1 e s l s d o 1 2 o o d h h t r s 1 2 g l l u u a a t e 1 1 e 1 m m e t t r 1 h h 2 1 1 2 1 2 Near Miss: A False Negative MCAD Screening Test Due To A Poor Quality Blood Spot
What can we do? Conclusions • The ENBS programme is not unsafe Analytical cut-offs generally well removed from 90 th centiles • Methionine is the exception but 2 nd tier testing is part of screening protocol • There is potential for false positives and unnecessary referral of babies and possibly false negatives • Harmonisation of ENBS should improve to maintain common cut-off values – common internal standard study • Co-ordination of approach at kit lot change - IRTs
Transport 2013/14
Results reporting Are the diagnostic (confirmatory) tests agreed? � Diagnostic protocol Are the results timely with clear metrics? � Quality dashboard Are the qualitative reports eg organic acids clear and unambiguous when they arrive? � No agreed standards in terms of layout or content � No training � No EQA or IQC � No user surveys � A variety of practice Can we support patients more effectively during this time of uncertainty? � Provision of information – an App with high quality information that is readily accessed � Thought about the processes of information receipt
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