Clinical toxicology: What? Who? How well is it done?

1
Clinical toxicology What? Who? How well is it
done?

• Dr Ian D Watson
• University Hospital Aintree
• LIVERPOOL L9 7AL

2
Laboratory Investigations

• Confirm poisoning diagnosis
• Patient management
• Investigations
• Antidotes or enhance elimination
• Brain death
• Re-start chronic therapy
• Medico-legal

3
UK Guidelines on Analytical Toxicology Practice

• Joint UK Guidelines National Poisons Information
  Service Association of Clinical Biochemists.
• Annals Clin. Biochem. 200239 328-339

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Recommended 24 hour chemistry test availability

• FBC
• Sodium, potassium, urea, creatinine
• Glucose
• Calcium, albumin, magnesium
• INR
• Bilirubin, ALT or AST, GGT, ALP
• Anion Gap (chloride and bicarbonate)
• Plasma osmolality (osmolar gap)
• Creatine kinase

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NPIS/ACB Toxicology Group12 hour turnaround 1

• Carboxyhaemoglobin
• Digoxin
• Ethanol
• Iron
• Lithium
• Methaemoglobin

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NPIS/ACB Toxicology Group12 hour turnaround 2

• Paracetamol
• Paraquat qualitative urine screen
• Salicylate
• Theophylline

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NPIS/ACB Toxicology Group 2Specialist Assays 1

• Acetylcholinesterase 6h
• Arsenic 24h
• Carbamazepine 2h
• Ethylene glycol 4h
• Lead 24h
• Mercury 24h
• Methanol 4h

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NPIS/ACB Toxicology Group 2Specialist Assays 2

• Methotrexate 24h
• Paraquat quantitative plasma assay 24h
• Phenobarbital 4h
• Phenytoin 2h
• Thyroxine 24h
• Toxicology screen as required

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Who?

• Specialist Toxicology laboratories 35
• General Clinical Biochemists with a Special
  interest in Toxicology 25
• General Clinical Biochemists 40

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How well is Toxicology done?

• Clinicians access to service
• NPIS/ACB turnaround times
• Analytical performance
• UKNEQAS data
• Quality of interpretation
• UKNEQAS Toxicology cases

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?Impact of NPIS/ACB advice

• Questionnaire via UKNEQAS for Drug Assays
  General Clinical Chemistry 2002 prior to
  publication of Guidelines
• Repeat questionnaire in early 2004,
• 18 months post publication

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Analytical performance 1
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Analytical Performance 2
14
Analytical Performance 3
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Routine 24 hour availability 1
16
Routine 24 h availability 2
17
Routine 24h availability 3
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Group 1 availability
On Site

19
Group 1 turnaround times

20
Group 1 turnaround timesout-of-hours

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Group 2 analyte availability 1

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Group 2 analyte turnaround time 1
In hours
23
Group 2 availability 2
On site
24
Group 2 availability 3
On Site

25
Group 2 turnaround times 3

26
Urine DOA availability
In hours

27
DOA turnaround times
In hours

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Mean Lab Score
Std. Dev 4.26 Mean 10.0 N 76.00
n
1.0 3.0 5.0 7.0
9.0 11.0 13.0 15.0
17.0
Score
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Mean lab score gt 4 samples
Std.Dev 4.06 Mean 9.9 N 48.00
n
1.0 3.0 5.0 7.0
9.0 11.0 13.0 15.0
17.0
Score
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Mean Score
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LABS MEAN SCORE OF LAST 4 SCORES
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Summary Count Sum Average Variance
1 31 278 8.97 15.77
2 31 318 10.26 55.73
3 31 367 11.84 12.74
4 31 323 10.42 16.72
5 31 333 10.74 15.60
6 31 287 9.26 14.73
7 31 322 10.39 37.38
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Observations

• Change following NPIS/ACB guidance
• Ethylene Glycol/Methanol service appears most
  improved
• Labs concentrate on the readily available.
• Analytical performance for unusual analytes poor
• Those that are poor interpreters are dropping out
  of Toxicology Case Scheme

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Other Issues

• Point of Care device performance and use needs
  assessed
• Toxicology Case scheme for Panel approval
• NPIS want standardisation of drug concentration
  units. How can we approach this?

35
Thanks to

• UKNEQAS for General Clinical Chemstry Dave
  Bullock and for Drug Assays John Wilson
• Michelle Robinson for secretarial assistance
• Rob Lewis for data handling
• Ceridwen Dawkins assisted with the audit
  formulation

36
Discussion arising from presentation 1

• Q Guideline turnaround times ACB weakly
  accepted with no Evidence Base
• A Comment only applies to Specialist assays.
  Those with 2h or 24h turnaround are either
  readily available eg phenytoin or are needed for
  differential eg mercury. Cholinesterase and
  methanol/ethylene glycol are metabolic
  emergencies.

37
Discussion arising from presentation 2

• Q Audience vote for which units.
• A majority abstained, of voters large majority
  for molar units. No strategy to address how to
  change, nor how to ensure adoption. Needs an
  evidence based approach?