Molecular identification of hepatitis B virus genotypes/subgenotypes: Revised classification hurdles and updated resolutions

Table 1 The misclassifications detected in hepatitis B virus subgenotyping

Genotypes	Subgenotypes old classification	Reasons (R) for misclassification					Suggested resolution	New proposed subgenotypes reclassification
A	A1, A2							A1, A2
	A3, A4, A5	R1	R2	R3		R5	Quasisubgenotype-A3	QS-A3
	A6							A4
	A7		R2	R3		R5	Quasisubgenotype-A3	QS-A3
B	B1, B2							B1, B2
	B3, B5, B7, B8, B9		R2	R3			Quasisubgenotype-B3	QS-B3
	B4							B4
	B6							B5
C	C1							C1
	C2			R3			Quasisubgenotype-C2	QS-C2
	C3							C3
	C4				R4		Trace recombination	RS-C4
	C5				R4		Trace recombination	RS-C5
	C6-C13							C6-C13
	C14		R2				Quasisubgenotype-C2	QS-C2
	C15, C16							C15, C16
	C/D1, C/D2				R4		Inter-genotypic recombinant	Not considered as subgenotype
D	D1, D2, D3		R2				Not decided yet
	D4, D5, D6, D7, D8, D9				R4		Recombino-subgenotype	RS-D4, RS-D5, RS-D6, RS-D7, RS-D8, RS-D9

Number (R1-R5) indicates the reason of problems in classification. R1: Applying partial gene in introducing subgenotype; R2: < 4% nucleotide divergence; R3: Weak bootstrap value or no monophyletic cluster; R4: Recombination; R5: Bias in reference collection. QS: Quasi-subgenotype; RS: Recombino-subgenotype.