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Paraquat

Chemical Pathology

Notes

Paraquat is a herbicide which was withdrawn from sale several years ago, however out-of-date preparations containing paraquat may still be available in home storage.

In all overdose situations clinicians should first access TOXBASE or contact the NPIS clinician who will indicate if analysis is required.

A qualitative urine test (dithionite spot test) should be performed urgently in all patients presenting with suspected paraquat poisoning to confirm exposure. This is available at Southmead Hospital, Bristol and can be accessed by contacting the duty biochemist either locally or direct via the Southmead switchboard and then once agreed, transporting samples urgently to Southmead.

There is no quantitative assay in blood available anywhere out of hours, however blood samples which may be useful for prognosis once a positive urine result has been observed, can be assayed by the Toxicology Laboratory at Llandough Hospital, Cardiff (Monday - Friday daytime only).

Sample requirements

For paraquat screen, a minimum of 5mL urine taken into a 30mL Universal

30ml universal container

If blood quantitation becomes necessary after confirmation of the presence of paraquat in urine:-

For adults, send blood taken into a 6mL lithium heparin tube.

6ml lithium heparin tube

For children, send blood taken into a 2mL lithium heparin tube

2ml lithium heparin BD paediatric tube

Storage/transport

Do not store. Send urine and blood samples immediately to the laboratory.

Required information

Relevant clinical details including date and time and nature of suspected ingestion, and date and time of sample collection.

Turnaround times.

Urine analysis is only available by arrangement with the duty biochemist (either direct via Southmead switchboard or via the local duty biochemist), in which case the samples will be assayed immediately on receipt in Southmead and results telephoned back.

Blood samples for paraquat levels (only after paraquat confirmed in urine) are sent for analysis to Llandough Hospital, Cardiff and results made available the same day (Monday to Friday).

Reference ranges

Qualitative urine screen is reported as positive or negative for the presence of paraquat. Blood levels are reported in mg/L.

Further information

To learn more about toxicology visit Lab Tests Online

National Poisons Information Service (NPIS) NHS clinical database TOXBASE

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