TABLE 2.

Performance of the 11/25 and/or net charge rule for genotypic prediction of CXCR4 coreceptor usage on HIV-1 molecular clones^a

Genotypic rule(s)	Expected phenotype	No. of clones with indicated phenotype		Sens (%)	Spe (%)	PPV (%)	NPV (%)
		R5	R5X4/X4
One basic residue at position 11 or 25	R5X4/X4	6	30	93.8	93	83.3	97.6
No basic residue at position 11 or 25	R5	80	2
Net charge of ≥+5	R5X4/X4	6	32	100	93	84.2	100
Net charge of <+5	R5	80	0
One basic residue at position 11 or 25 and net charge of ≥+5	R5X4/X4	0	30	93.8	100	100	97.6
No concomitant basic residue at position 11 or 25 and net charge of ≥+5	R5	86	2

^aBasic residues refer to amino acids R and K. Sens, sensitivity; Spe, specificity; PPV, positive predictive value; NPV, negative predictive value.