Published estimates of CD4 cell count decay rate and variability in untreated HIV-infected individuals.

Parameters derived from linear mixed effect model in the square root scale. β: slope and σb: inter-individual slope variability in (106/L)0.5/year; α: intercept, σa: inter-individual intercept variability and σe: intra-individual variability in (106/L)0.5; ρab: correlation between α and β; N: number of individuals, n: average number of samples per individual; average duration of observation in years.
*slope according to age (15–20: 1.30, 20–30: 1.53, 30–40: 1.73, >40: 1.67) and to symptoms at pre-infection (present: +0.26).
°intercept depending on subgroup (sex, age, intravenous drug use or haemophilia).
†slope depending on viral load (0 at <103, then 0.016, 0.04, 0.12, 0.4, 0.8 and 1.6 for every 100.5 step up to 2.0 at >106/mL), age (+0.007/year), X4-virus shift (present: +0.25).
‡slope depending on age (<35: 1.3, >35: 2).
**standard deviation of an uniform distribution in the untransformed CD4 count scale.
°°outlier value discarded from average calculation.