Table 1.

Performance of previously published Fiebig and 4^th gen staging systems

Model and stage	Specimens	Predicted and observed times after first viremia (DDI₁₀₀) for each stage
		Predicted time	Distribution of actual times observed		Error in model estimates
	N/n		Median	[25^th,75^th] IQR	RMS difference (predicted-observed)
Fiebig (after Fiebig, et al., 2003)²
Stage 1 RNA+ p24− 3G−	30/62	9 days	9 days	[8,12] days	3.5 days
Stage 2 RNA+ p24+ 3G−	29/55	15	16	[14,19]	3.1
Stage 3 RNA+ p24+ 3G+ 2G/WB−	15/27	19	20	[20,23]	4.5
Stage 4 RNA+ WB indeterminate	10/18	23	27	[22,30]	6.8
Stage 5 RNA+ WB+ (p31−)	8/54	61	35	[30,41]	26.2
Stage 1-2^* RNA+ 3G−	31/117	12	13	[9,16]	7.7
Stage 1-3^* RNA + Ab rapid test−	31/144	13	14	[10,20]	7.8
Stage 1-4^* RNA + unspecified Ab−	31/162	17	15	[11,21]	10.5
4^th Gen (after Ananworanich, et al. 2013)¹
Stage 1 RNA+ 4G− 3G−	30/64	9	9	[8,12]	3.4
Stage 2 RNA+ 4G+ 3G−	28/53	19	16	[14,19]	4.0
Stage 3 RNA+ 4G+ 3G+ WB indeterminate	18/45	22	23	[21,27]	5.4

Abbreviations: 3G = 3^rd Generation (IgM-sensitive antibody assays); 4G = 4^th Generation (p24 antigen/antibody assays); RMS = root mean square; IQR = interquartile range; DDI₁₀₀ = days since detectable infection on a 100-copy viral load; N = unique individuals; n = specimens from distinct timepoints

Because it is often impossible to determine the precise Fiebig stage, examples are also given for the infection times seen for combinations of stages which can sometimes be inferred from ‘incomplete’ staging information