Health consequences of exposure to aircraft contaminated air and fume events: a narrative review and medical protocol for the investigation of exposed aircrew and passengers

Table 1 Blood sampling for acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and neuropathy target esterase (NTE)

Method	Enzyme	Half-life (days)	Sample 1 (Time after incident)	Sample 2 (Baseline) (Time after incident)	Sample details
Enzyme assay	AChE—Red blood cell (RBC)	33	Preferably 4 – 48 h	2–3 months ^a	Standard protocol^g
	BChE—Plasma	12	Preferably 4 – 24 h	1–2 months ^a	Standard protocol^g
	NTE^e (lymphocytic)	5–7		2–3 months ^a	Standard protocol^e – Only fresh blood can be analysed ^c
Mass spec analysis^f	Cresylphosphate - modified butyrylcholinesterase				Plasma should be stored till a routine measurement is available
	AChE	33	4 h – 2 weeks	One sample required only ^b	4 × 6 ml in EDTA tubes ^d
	BChE	12	4 h – 1 week	One sample required only^b	4 × 6 ml in EDTA tubes ^d

^aA second sample to be undertaken as a baseline. AChE recovers to normal level after around two to three months, while BChE recovers after around one to two months. If symptoms alleviate before this time, undertake a baseline sample before returning to work or when away from further exposures. It is preferable to undertake a baseline before starting flying employment
^bStore locally at present
^cNTE analysis: Only fresh blood can be used
^dSeparate (centrifuge) plasma and red cells and store separately at -20^OC to –80 °C locally. Assays preferably tested in triplicate within the same laboratory with 5% range
^eNTE blood analysis is not routinely available
^fStill research study at this time. Assessing the percentage modification of AChE, BChE or other esterases using mass spectrometry
^gBaseline AChE and BChE values for OP exposures have been generally determined for very high agricultural exposures, but not for aircraft fume event exposures and may not be sensitive enough for the latter. However, we measure them to get more data and experience about its diagnostic value. Note that there is a wide variation between individual baseline levels and therefore it is the 30–70% inhibition below the individual baseline that is the important reference. Each laboratory will use differing reference levels. Reference levels do not take into account the individual variation, which is the most important factor when analysing biomarkers as an indicator of OP exposure, as outlined above

ISSN: 1476-069X