Assessment of patient complexity using routinely collected data: The UK CHIC study

We identified predictors of clinical complexity based on data collected in the UK CHIC Study. All subjects under established care (>1 year) from 2000-2010 were included. Each subject’s follow-up (1 year after study entry to last clinic visit, death or 31/12/2010) was stratified into a series of 6-monthly periods and his/her status was assessed at the start of each. Using Poisson regression (with generalised estimating equations to allow for multiple entries per subject), we studied associations between demographic/clinical factors, CD4 count/percent, viral load (VL), calendar year and measures of prior/current antiretroviral (ART) use, and the development of a new AIDS event or death during each period. A complexity score was derived from the coefficients of the final model; subjects were categorised into ten equally sized groups based on the score, and event rates were calculated for each group. The 31,338 eligible subjects had a median (interquartile range) age of 36 (10, 42) years at baseline. Ethnicity was white (55%), black African (27%), black other (5%), other (9%) and unknown (4%). Mode of acquisition was sex between men (52%), heterosexual sex (37%), other (5%) and unknown (5%). Subjects contributed a total of 377,284 periods of follow-up (181,170 person-years [PY]) of which 5796 included a clinical event (rate/1000 PY: 3.20 [95% confidence interval 3.12, 3.28], 4322 AIDS events, 1534 deaths). As an active AIDS-defining event in the past 6 months was the dominant predictor of a new clinical event (relative rate 41.55), subjects with an active event were excluded from further analysis. Risk factors for a clinical event in patients without an active AIDS event (Table 1) were earlier calendar year, non-white ethnicity, older age, lower CD4 count, >80 CD4 cell drop from previous visit, being off ART or on ART with a VL >10,000 copies/ml. Hepatitis co-infection and previous experience of immune suppression were associated with lower clinical risk. A score based on this model discriminated reasonably well between subjects who did/did not develop an endpoint over the next 6 months (approximate C-statistic: 0.72), with event rates increasing from 0.49/100 PY in the lowest score group to 7.16/100 PY in the highest. A score based on clinical markers may provide a means to identify those who will experience clinical progression over the next 6 months, allowing this group to be targeted for closer monitoring and funds for HIV care to be distributed appropriately. (Published: 11 November 2012) Citation: Abstracts of the Eleventh International Congress on Drug Therapy in HIV Infection Sabin C and Delpech V. Journal of the International AIDS Society 2012, 15 (Suppl 4):18133 http://www.jiasociety.org/index.php/jias/article/view/18133 | http://dx.doi.org/10.7448/IAS.15.6.18133