An inter-laboratory study of DNA-based identity, parentage and species testing in animal forensic genetics

Figures & data

Table 1. Details on DNA test samples included in the 2016 and 2018 animal forensic comparison tests (AFCTs).

AFCT	Sample	Species	Purpose^a	Quality	Concentration (volume)
2016	1	Canis lupus familiaris	M	Undiluted	25 ng/µL (50 µL)
	2	Canis lupus familiaris	M	Diluted	150 pg/µL (50 µL)
	3	Canis lupus familiaris	M	Undiluted	25 ng/µL (50 µL)
	4	Bos taurus	S	Undiluted	50 ng/µL (50 µL)
2018	1	Canis lupus familiaris	M	Diluted	300 pg/µL (30 µL)
	2	Canis lupus familiaris	M	Undiluted	50 ng/µL (30 µL)
	3	Canis lupus familiaris	M	Undiluted	50 ng/µL (30 µL)
	4	Canis lupus familiaris	P	Undiluted	10–20 ng/µL (30 µL)
	5	Canis lupus familiaris	P	Undiluted	10–20 ng/µL (30 µL)
	6	Canis lupus familiaris	P	Undiluted	10–20 ng/µL (30 µL)
	7	Bos taurus	S	Undiluted	50 ng/µL (30 µL)
	8	Gadus morhua	S	Undiluted	50 ng/µL (30 µL)

^aM and P indicate dog DNA samples designated for forensic identification and parentage tests, respectively; S indicates DNA from an unknown species for species determination.

Table 2. The percentage of relative genotyping accuracy values for each STR in Panel 1.1 and the core ISAG panel were estimated as the ratio between the concordant genotypes and reported genotypes for the 2016 and 2018 AFCTs, respectively.

	Relative genotyping accuracy (%)
Marker name	2016 AFCT	2018 AFCT
AHT121*	93.83	94.51
AHT137*	70.80	96.70
AHTh130	100.00	92.54
AHTh171*	83.30	91.21
AHTh260*	88.20	91.21
AHTk211*	83.30	92.31
AHTk253*	94.10	100.00
CXX0279*	88.90	91.21
FH2054*	88.90	89.25
FH2848*	94.10	85.71
INRA021*	72.20	91.21
INU005*	72.20	88.37
INU030*	83.30	91.21
INU055*	83.30	91.21
REN105L03	70.00	89.47
REN162C04*	88.90	95.60
REN169D01*	88.20	95.35
REN169O18*	88.90	95.60
REN247M23*	83.30	91.21
REN54P11*	77.80	94.51
REN64E19	100.00	93.42

*The 18 STRs in Panel 1.1 that are part of the core ISAG panel.

Table 3. Comparison of average absolute (Aga) and relative genotyping accuracy (Rga) estimates among laboratories (%, mean±SD).

Subject	2016 AFST			2018 AFST
n	Rga%	Aga%	n	Rga%	Aga%
Government/academy	8	77.25±31.79	66.36±27.36	11	91.78±26.06	85.70±28.31
Private	10	97.87±2.66	92.97±6.62	8	89.67±17.71	89.67±20.34

Absolute (Aga) and relative (Rga) values for the short tandem repeats (STRs) included in the International Society for Animal Genetics (ISAG) core panel as well as the Canine Genotypes™ Panel Kit 1.1 (Thermo Fisher Scientific) using ISAG’s formula for STR typing comparison tests (https://www.isag.us/docs/Rules_CT.pdf?v2).

Aga% = (total number of expected genotypes − genotyping errors including no genotype reported)/total number of genotypes.

Rga% = (the number of genotypes reported − total number of genotype errors excluding blanks)/the number of genotypes reported.

Table 4. Percentage of different types of genotyping errors in each animal forensic comparison test (AFCT)*.

AFCT	Missing data (%)			Loading error (%)		False homozygotes (%)	False heterozygotes (%)	Incorrect genotypes (%)
	STR blanks	Sample blanks	Genotype blanks	Typing errors	Nomenclature errors
2016	33.33	0.00	4.76	2.38	15.48	5.95	5.95	32.14
2018	20.48	15.02	15.02	19.45	6.14	2.73	0.68	20.48
Total	25.16	9.54	11.30	13.23	9.54	3.90	2.60	24.73

*Percentages might not total 100% due to rounding.