Analytical Laboratory Testing
Considering the type of poisonings prevalent in the area, laboratory investigations have been standardized with the voluntary support of experienced biochemists and chemists. Only those tests which are relevant, economical and have a quick turnaround time, and those which make a difference in emergency management of poisoning, have been developed.
All tests are done with standard laboratory reagents. Methods used are:High Performance Liquid Chromatography (HPLC), Thin-layer-chromatography (TLC), Spectorphotometry, Analysis by Toxi-Lab system, immuno-assay and color tests for qualitative analysis. The tests have been adapted from standard text books and peer-reviewed journals.
Following tests were found to fulfill the above criteria:
| Plasma and RBC cholinesterase levels in Blood samples: | Plasma cholinesterase levels are easily available. However, RBC cholinesterase is a better indicator of severity of OP poisoning. This test has been specially developed and standardized in the CEARCH laboratory. | ||||||||||
| Blood Lead levels by Lead Care II Analyzer (USFDA approved) |
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| Drug screening for drugs of abuse (From biological samples): | This has been found to be especially useful for patients with altered sensorium and drugs like benzodiazepines. Confirmation is done with TLC and UV scanning. This has been found to be especially useful for patients with altered sensorium and drugs like benzodiazepines. Confirmation is done with TLC and UV scanning. |
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| Detection by Color tests from urine/gastric lavage samples: | These tests are done for detection of acetaminophen (paracetamol), salicylic acid, phenothiazines, imipramine, ethanol and other volatile reducing agents, phenol, thiocyanates, paraquat, Phosphorous & phosphides, mercury (G. lavage). | ||||||||||
| Blood paracetamol Level: | Blood levels of paracetamol are estimated after four hours of overdose to decide about the need for N-acetyl cysteine (as per Rumack-Mathew Nomogram). | ||||||||||
| Blood levels of salicylates, Methemoglobin, Thiocyanate and copper: | Blood levels of these compounds are also estimated in poisoning cases. | ||||||||||
| Unknown drug analysis using Toxi-Lab system: |
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| Drug analysis Using HPLC: | HPLC is considered as the 'Gold Standard' among analytical techniques. It is used for accurate estimation of drugs useful both for Therapeutic Drug Monitoring (TDM) and drug overdose.
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Guideline for sample collection etc:
Tests useful for the management of acute poisoning cases |
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| Test | Method | Sample | Turn Around Time after reaching the toxicology lab. (TAT) | ||
| Requirement | Collection | Transport | |||
| RBC Cholinesterase activity | Spectrophotometry | 3 ml EDTA Blood | After suspecting pesticide poisoning | 2 -8℃ | 1 hour |
| Plasma Cholinesterase activity | Spectrophotometry | 3 ml EDTA Blood /1 ml non-hemolyzed serum | After suspecting pesticide poisoning | 2 -8℃ | 1 hour |
| Blood Paracetamol level | Spectrophotometry | 3 ml EDTA Blood / 1 ml serum | Blood collection at least 4 hours after ingestion; the time of 'drug ingestion' and 'blood collection' to be mentioned | 2 -8℃ | 2 hour |
| Serum Salicylate level | Spectrophotometry | 3 ml plain Blood | After suspecting pesticide poisoning | 2 -8℃ | 2 hours |
| Blood Methemoglobin level | Spectrophotometry | 3 ml plain Blood | Blood collection in air tight tube/container to prevent exposure to air | 2 -8℃ | 1 hours |
| Serum/ Urine Copper | Spectrophotometry | 3 ml EDTA Blood / 1 ml serum | Acid washed container to be used for Urine | 2 -8℃ | 1 hours |
| Serum/Plasma Thiocyanate | Spectrophotometry | 3 ml EDTA Blood / 1 ml serum | After suspecting poisoning | 2 -8℃ | 1 hours |
NB: The sample should be sent as early as possible for above tests |
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Other tests for Toxic exposures |
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| Test | Method | Sample | TAT | ||
| Requirement | Collection | Transport | |||
| Blood (serum) Alcohol Level | Enzymatic method using Spectrophotometry | 1 ml Serum/Plasma | Do not use Alcohol swab during blood collection | 2 -8℃ | 2 hours |
| Urine Color Test for Common drugs& other toxicants (Screen-1) | Color test (for Salicylic Acid, Phenothiazines, Paracetamol, Imipramine & related Comps, Phenol, Paraquat,Thiocyanate) | 20ml fresh Urine sample | Immediately after suspecting toxic exposure | 2 -8℃ | 2 hours |
| Drug of abuse (9 drugs) in Urine (Screen-2) | Strip Immunoassay | 20ml fresh Urine sample | Immediately after suspecting drug | 2 -8℃ | 1 hours |
| Urine drug screening (by Screen-1 & -2) | Color test + Strip Immunoassay | 20ml fresh Urine sample | Immediately after suspecting drug | 2 -8℃ | 2 hours |
| Urine drug (26 drugs) screening (by Toxilab A) | TLC (Thin Layer Chromatography) | 20ml fresh Urine sample | Immediately after suspecting drug | 2 -8℃ | 3 hours |
| Gastric lavage for suspected pesticides | TLC | 30-40 ml G. Lavage | The suspected pesticide ingested by patient should be sent with G. lavage | - | 6 hours |
| Gastric lavage for drugs | TLC | 30-40 ml G. Lavage | The suspected drug ingested by patient should be sent with G. lavage | - | 6 hours |
| Gastric lavage Color Test for Common drugs& other toxicants | Mercury, Salicylic Acid, Phenothiazines, Paracetamol, Imipramine | 30-40 ml G. Lavage | Immediately after suspecting toxic exposure | 2 -8℃ | 3 hours |
| Blood Lead level | Electrochemical | 2 ml EDTA or Heparin blood | Wear powder-free gloves to prevent lead contamination. | 2 -8℃ | 1 hours |
| Urine Delta-Aminolevulinic Acid (δ-ALA) | Spectrophotometry | 20 ml Urine | Wrap Container with Aluminium foil or use to brown bottle to protect the container from light | 2 -8℃ | 4 hours |
| Urine δ-ALA and Porphobilinogen (Combined) | Column chromatography & Spectrophotometry using 'ClinRep' kit | 20 ml Urine(add this row) | Wrap Container with Aluminium foil or use to brown bottle to protect the container from light | 2 -8℃ | 4 hours |
| Urine Phenol | Spectrophotometry | 20 ml Urine | 2 -8℃ | 4 hours | |
| Detection of common Steroids in unknown drug preparation | TLC (for betamethasone, dexamethasone, deflazacort, prednisolone, methyl prednisolone) | Alternative medicine/powders | 6 hours | ||
NB: Above tests can be done after 2-3 days of sample collection with proper storage |
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Tests done on HPLC [Useful for Therapeutic Drug Monitoring and drug overdose] |
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| Drug | Test | Sample Requirement | TAT | ||
| Antifungal drugs | Blood Voriconazole Level | 1ml Separated Plasma/Serum | 6 hours | ||
| Blood Posaconazole Level | 1ml Separated Plasma/Serum | 6 hours | |||
| Antibiotic level | Blood Vancomycin Level | 1ml Separated Plasma/Serum | 6 hours | ||
| Antiepileptic Drugs-I | Phenobarbitone, Phenytoin, Carbamazepine & its epoxide, Oxcarbazepine & its mono-Hydroxy metabolite | 1 ml Separated Serum | 5 hours | ||
| Other Antiepileptic Drugs-II | Ethosuximide, Carbamazepine, Carbamazepine-epoxide, Ethosuximide, 10-Hydroxy-Carbamazepine, Lamotrigine, Oxcarbazepine, Phenobarbital, Phenytoin, Primidone, Sulthiame | 1 ml Separated Serum | 6 hours | ||
| Other Antiepileptic Drugs-III | Lacosamide, Zonisamide, Felbamate, Rufinamide, N-Desmethylmethsuximide | 1ml Separated Plasma/Serum | 6 hours | ||
| Other Antiepileptic Drugs-IV | Blood Levetiracetam | 1ml Separated Plasma/Serum | 6 hours | ||
| NB: (i) Blood/Serum must not be hemolyzed and Gel tubes not be used which cause interference in HPLC analysis. Blood should be collected; serum/plasma separated as soon as possible and stored properly or transported at 2 -8℃. (ii) For trough Level of the drug, collect the sample before the next dose. |
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