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Emphysema Progression Similar With HIV
and in Older HIV-Negative Heavy Smokers
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6th International Workshop on HIV and Aging
October 5-6, 2015, Washington, DC
Mark Mascolini
Emphysema progression rate in an Italian HIV cohort proved similar to the rate in a 14-year older general-population cohort whose members smoked more [1]. In the HIV group baseline emphysema score, distribution, and carbon monoxide diffusing capacity (DLCO) predicted emphysema progression, but spirometry results did not. More than 15% of these people with HIV had emphysema progression in about 3 years.
Evidence suggests that HIV-positive people "have a propensity to develop emphysematous changes in their upper lobes at an accelerated rate independent of smoking status" [2]. Because little is known about predicting progression of emphysema with HIV, or about how progression rates in HIV populations compare with rates in the general population, researchers in Italy and Canada conducted this two-part study.
At the Modena HIV Metabolic Clinic, 345 adults had baseline and follow-up chest CTs. These were patients in routine care and were not selected because of respiratory symptoms. Two radiologists read the images blindly and assigned a score to each of the 5 lobes and the lingula--0 for no emphysema, 1 for 1% to 25% emphysema, 2 for 26% to 50%, 3 for 51% to 75%, and 4 for 76% to 100%. Researchers summed scores to create a total score for each patient; they defined progression as any increase in total score over the study period. Next the investigators matched members of the HIV group by sex and interval between first and last CTs with members of the Pan-Canadian Early Detection of Lung Cancer Study.
In the HIV group median interval between first and last CT stood at 3.36 years (interquartile range [IQR] 2.07 to 4.99). Median age stood at 49 (IQR 45 to 53), median body mass index at 23.8 kg/m2, and median current CD4 count at 577. Most participants (90%) were men, 77% had a viral load below 40 copies, 48% currently smoked, and 29% formerly smoked. Spirometry results were largely normal.
Of the 345 patients, 60 (17%) had CT evidence of progressive emphysema. Univariate analysis identified four factors associated with progressive emphysema: (1) more severe baseline emphysema score, (2) both centrilobular and paraseptal emphysema distribution (versus just centrilobular or paraseptal distribution), (3) currently smoking more than 10 cigarettes daily, and (4) having a lower baseline diffusion capacity (DLCO).
In multivariate analysis two factors independently predicted emphysema progression--having both centrilobular and paraseptal emphysema distribution on the baseline CT (estimate 0.241, P = 0.013) and low baseline DLCO (-0.004, P = 0.0005). Three factors combined--baseline emphysema score, baseline emphysema distribution, and baseline DLCO had an area under the curve (AUC) of 0.85 for predicting emphysema progression. In contrast, AUC was only 0.65 for baseline spirometry-determined FEV1/FVC and only 0.54 for baseline FEV1% predicted.
The researchers then matched 301 HIV-positive people by sex and interval between first and last CT to 301 HIV-negative people in the Canadian cancer-screening cohort. Compared with the general-population Canadian group, people with HIV were significantly younger (median age 49 versus 63, P = 2.2[e-16]), included a larger proportion who never smoked (21% versus 0%, P = 2.2[e-16]), and smoked fewer pack-years (17 versus 50 pack-years, P = 2.2[e-16]). Despite these lung advantages in the HIV group, rates of emphysema proved similar in people with HIV (46 people, 15%) and in the general-population group (52 people, 17%) (P = 0.58).
The researchers concluded that HIV-positive people who are younger and smoke less than HIV-negative people may have a similar rate of emphysema progression. They proposed that combined emphysema severity score, distribution, and diffusion capacity may be useful in "to identify high-risk patients in need of aggressive smoking cessation programs and chronic obstructive pulmonary disease treatments."
References
1. Leung J, Malagoli A, Santoro A, et al. HIV patients exhibit similar rates of emphysema progression observed in older HIV-uninfected patients with higher cumulative smoke exposure. 6th International Workshop on HIV and Aging. October 5-6, 2015, Washington, DC. Abstract 11.
2. Petrache I, Diab K, Knox KS, et al. HIV associated pulmonary emphysema: a review of the literature and inquiry into its mechanism. Thorax. 2008;63:463-469. http://thorax.bmj.com/content/63/5/463.long
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