Page Last Updated: October 10, 2025

USDTL Nails Toxicology (Maternal)🔗

Table Name:

bio_bm_biosample_nails_results (toxicology screen), bio_bm_biosample_nails_type (specimen type)

Construct:

Drug, Environmental Exposure

Continuous Variables
For all toxicology screens, continuous variables should be interpreted with caution based on the threshold limits of quantification (LOQs), or the cutoff concentration used to categorize metabolites as positive or negative. LOQs are provided in Table 1. Nail Assay Thresholds.

Updated Workflow
As of July 1, 2024, the nail processing workflow was updated to optimize specimen use and allow confirmation testing for low sample quantities. Prior to this update, remnants of ELISA extract were not used for confirmation when specimens had insufficient sample.

Administration & Quality Control🔗

Respondent	Pregnant/postpartum person
Administration	Self-collected under research team supervision, or collected by research team
Visits	V01, V02
Completion Time	5 min
Quality Control	Examine assay ranges and categorical versus continuous measures.

Instrument Details🔗

For the USDTL assay, fingernail and toenail specimens are sorted by weight, and those weighing at least 20 mg undergo ELISA screening, followed by LCMSMS confirmation for presumptive positives, each requiring an additional 20 mg. If insufficient specimen remains for LCMSMS, the remnant ELISA extract is used for confirmation.

Based on the predefined threshold outlined in Table 1, a confirmatory test result for any substance analyte is determined to be positive, negative, or invalid (QNS i.e. quantity not sufficient). Substance analytes (e.g. Amphetamine (c_amp_n)) are grouped into different classes by analyte screening tests and confirmatory tests (Table 2).

Analyte	LOD Limit of detection (pg/mL)	LOQ Limit of quantification (pg/mL)	Cutoff (pg/mL)	Detection Window (months)
Amphetamine	20	40	100	Finger 3-6; Toe 10-14
Methamphetamine	20	40	100	Finger 3-6; Toe 10-14
MDA	20	40	100	Finger 3-6; Toe 10-14
MDMA	20	40	100	Finger 3-6; Toe 10-14
MDEA	20	40	100	Finger 3-6; Toe 10-14
Carboxy-delta-9-THC	0.01	0.02	0.05	Finger 3-6; Toe 10-14
Cocaine	20	40	100	Finger 3-6; Toe 10-14
Cocaethylene	10	20	50	Finger 3-6; Toe 10-14
Benzoylecgonine	10	20	50	Finger 3-6; Toe 10-14
Norcocaine	10	20	50	Finger 3-6; Toe 10-14
6-MAM	20	40	100	Finger 3-6; Toe 10-14
Codeine	20	40	100	Finger 3-6; Toe 10-14
Hydrocodone	20	40	100	Finger 3-6; Toe 10-14
Hydromorphone	20	40	100	Finger 3-6; Toe 10-14
Morphine	20	40	100	Finger 3-6; Toe 10-14
Norhydrocodone	8	16	40	Finger 3-6; Toe 10-14
Oxycodone	20	40	100	Finger 3-6; Toe 10-14
Oxymorphone	20	40	100	Finger 3-6; Toe 10-14
Noroxycodone	8	16	40	Finger 3-6; Toe 10-14
Methadone	20	40	100	Finger 3-6; Toe 10-14
EDDP	20	40	100	Finger 3-6; Toe 10-14
Amobarbital	80	80	200	Finger 3-6; Toe 10-14
Butalbital	80	80	200	Finger 3-6; Toe 10-14
Pentobarbital	80	80	200	Finger 3-6; Toe 10-14
Phenobarbital	80	80	200	Finger 3-6; Toe 10-14
Secobarbital	80	80	200	Finger 3-6; Toe 10-14
Alprazolam	20	40	100	Finger 3-6; Toe 10-14
Diazepam	20	40	100	Finger 3-6; Toe 10-14
Midazolam	20	40	100	Finger 3-6; Toe 10-14
Nordiazepam	20	40	100	Finger 3-6; Toe 10-14
Oxazepam	20	40	100	Finger 3-6; Toe 10-14
Temazepam	20	40	100	Finger 3-6; Toe 10-14
Ketamine	20	40	100	Finger 3-6; Toe 10-14
Norketamine	20	40	100	Finger 3-6; Toe 10-14
Tramadol	200	400	500	Finger 3-6; Toe 10-14
Fentanyl	2	4	10	Finger 3-6; Toe 10-14
Norfentanyl	2	4	10	Finger 3-6; Toe 10-14
Alfentanil	2	4	10	Finger 3-6; Toe 10-14
Acetyl Fentanyl	2	4	10	Finger 3-6; Toe 10-14
Acetyl Norfentanyl	2	4	10	Finger 3-6; Toe 10-14
Sufentanil	1	2	5	Finger 3-6; Toe 10-14
Norsufentanil	2	2	5	Finger 3-6; Toe 10-14
Buprenorphine	4	8	20	Finger 3-6; Toe 10-14
Norbuprenorphine	4	8	20	Finger 3-6; Toe 10-14
Ethyl glucuronide	4	8	20	Finger 3; Toe no consensus
Nicotine	20	40	100	Finger 3-6; Toe 10-14
Cotinine	20	40	100	Finger 3-6; Toe 10-14

Class	Screening Test	Confirmatory Test
Stimulant (`c_any_stim_n`)	amp/mamp (`s_amp_n, s_mamp_n`)	Amphetamine (`c_amp_n`)
		Methamphetamine (`c_meth_n`)
		MDMA (`c_mdma_n`)
		MDA (`c_mda_n`)
		MDEA (`c_mdea_n`)
	coc (`s_coc_n`)	Cocaine (`c_coc_n`)
		Cocaethylene (`c_cocae_n`)
		Benzoylecgonine (`c_ben_n`)
		Norcocaine (`c_ncoc_n`)
Cannabinoid (`c_any_cannabinoid_n`)	thc (`s_thc_n`)	Carboxy-delta-9-THC (`c_delta-9-THC_n`)
Barbiturate (`c_any_barb_n`)	bar (`s_bar_n`)	Amobarbital (`c_amobarb_n`)
		Secobarbital (`c_secobarb_n`)
		Pentobarbital (`c_pentobarb_n`)
		Phenobarbital (`c_phenobarb_n`)
		Butalbital (`c_butalbital_n`)
Benzodiazepine (`c_any_benzo_n`)	benz (`s_benz_n`)	Diazepam (`c_diaz_n`)
		Oxazepam (`c_oxaz_n`)
		Nordiazepam (`c_nord_n`)
		Temazepam (`c_tema_n`)
		Midazolam (`c_mida_n`)
		Alprazolam (`c_alpa_n`)
Opioids (`c_any_opioid_n`)	opi (`s_opi_n`)	Codeine (`c_cod_n`)
		Morphine (`c_mor_n`)
		MAM (`c_mam_n`)
		Hydrocodone (`c_hydroc_n`)
		Norhydrocodone (`c_norh_n`)
		Hydromorphone (`c_hydrom_n`)
	mtd (`s_mtd_n`)	Methadone (`c_mtd_n`)
	mtd (`s_mtd_n`)	EDDP (`c_eddp_n`)
	oxyc (`s_oxyc_n`)	Oxycodone (`c_oxyc_n`)
		Noroxycodone (`c_noxyc_n`)
		Oxymorphone (`c_oxym_n`)
	tram (`s_tram_n`)	Tramadol (`c_tram_n`)
	fent (`s_fent_n`)	Fentanyl (`c_fent_n`)
		Norfentanyl (`c_nfent_n`)
		Acetylfentanyl (`c_acfent_n`)
		ActlNorfentanyl (`c_acnfent_n`)
	suf (`s_suf_n`)	Alfentanil (`c_afent_n`)
		Sufentanil (`c_suf_n`)
		Norsufentanil (`c_nsuf_n`)
	bup (`s_bup_n`)	Buprenorphine (`c_bup_n`)
	bup (`s_bup_n`)	Norbuprenorpine (`c_nbup_n`)
dissociative anesthetic (`c_disanesth_n`)	ket (`s_ket_n`)	Ketamine (`c_ket_n`)
dissociative anesthetic (`c_disanesth_n`)	ket (`s_ket_n`)	Norketamine (`c_nket_n`)
Nicotine (`c_nicotine_n`)	cot (`s_cot_n`)	Nicotine (`c_nic_n`)
Nicotine (`c_nicotine_n`)	cot (`s_cot_n`)	Cotinine (`c_cot_n`)
Ethanol (`c_ethanol_n`)		ethyl glucuronide (`c_etoh_n`)

Final results for each substance follows these rules:

If the confirmatory test for any substance analyte (e.g. Amphetamine (c_amp_n)) is positive based on predefined thresholds (Table 1), the class-level (c_any_stim_n) and sample-level (c_any_specimen_n) are also positive (value =1).
Otherwise, if the substance analyte confirmatory tests are negative, then class-level are negative (value =0). If all classes are negative (value = 0), then sample-level (c_any_specimen_n) are negative (value = 0).
Finally, if any substance analyte confirmatory tests are invalid (value = 3) then that class-level, and sample-level values are also invalid (value = 3)

Table 3. Screening Result Scoring

Level	Result Type	Example	Options
Specimen	Confirmatory results (presence of any analyte)	`c_any_specimen_n`	`1`=positive; `0`=negative; `3`=invalid
Class	Confirmatory results (presence of any analyte in class)	`c_any_stim_n`	`1`=positive; `0`=negative; `3`=invalid
Analyte	Screening results	`s_amp_n`	`1`=positive; `0`=negative; `3`=invalid
	Confirmatory results	`c_amp_n`	concentration value; -999
	Confirmatory results - categorical	`c_amp_n_cat`Categorical confirmatory test variable for alcohol follows a different convention and is ‘c_ethanol_n’	`1`=positive; `0`=negative; `3`=invalid; `4`=screen negative

References🔗

Bandoli, G., Anunziata, F., Bogdan, R., Zilverstand, A., Chaiyachati, B. H., Gurka, K. K., Sullivan, E., Croff, J., & Bakhireva, L. N. (2024). Assessment of substance exposures in nail clipping samples: A systematic review. Drug and Alcohol Dependence, 254, 111038. https://doi.org/10.1016/j.drugalcdep.2023.111038

Sullivan, E. L., Bogdan, R., Bakhireva, L., Levitt, P., Jones, J., Sheldon, M., Croff, J. M., Thomason, M., Lo, J. O., MacIntyre, L., Shrivastava, S., Cioffredi, L.-A., Edlow, A. G., Howell, B. R., Chaiyachati, B. H., Lashley-Simms, N., Molloy, K., Lam, C., Stoermann, A. M., … HBCD Biospecimens Workgroup. (2024). Biospecimens in the HEALthy Brain and Child Development (HBCD) study: Rationale and protocol. Developmental Cognitive Neuroscience, 70(101451), 101451. https://doi.org/10.1016/j.dcn.2024.101451