OBJECTIVES: A survival analysis was conducted on patients with COPD receiving long-term oxygen therapy (LTOT) to compare two different statistical methods. METHODS: We used a multivariate crude (observed) survival model (Cox) and a multivariate relative survival model (Hakulinen). Only the latter is able to correct the survival by adjusting it to the normal life expectancy of the studied patients. PATIENTS: Two hundred fifty-two hypoxemic COPD patients (207 male) requiring LTOT were included. Mean PaO2 was <50 mm Hg before oxygen therapy. Mean age was >69 years (SE: 9.9). They had severe bronchial obstruction: mean FEV1 was <33% (10.6) of predicted values, with some CO2 retention: mean PaCO2 was 45.6 (7.1) mm Hg. By December 31, 1995, 189 patients had died (75%) and 13 (5%) were unavailable for follow-up. RESULTS: The overall crude survival was poor: 80.9% after 1 year, 67.1% after 2 years, 34.7% after 5 years, and 7.1% after 10 years. In the crude multivariate analysis (Cox), the negative prognostic factors were age and hypercapnia. The overall relative survival (Hakulinen), corrected for life expectancy, was 82.8% after 1 year, 70.8% after 2 years, 41.5% after 5 years, and 10.25% after 10 years. In the final multivariate relative model, age was no longer significant and the only bad prognostic factor was hypercapnia with a relative risk of 1.97 (1.16 to 3.34). CONCLUSION: This work shows the inadequacy of the Cox observed survival model when it comes to appreciating the real prognostic impact of age, because of the confusing factor associated with a normal life expectancy.
OBJECTIVES: A survival analysis was conducted on patients with COPD receiving long-term oxygen therapy (LTOT) to compare two different statistical methods. METHODS: We used a multivariate crude (observed) survival model (Cox) and a multivariate relative survival model (Hakulinen). Only the latter is able to correct the survival by adjusting it to the normal life expectancy of the studied patients. PATIENTS: Two hundred fifty-two hypoxemic COPDpatients (207 male) requiring LTOT were included. Mean PaO2 was <50 mm Hg before oxygen therapy. Mean age was >69 years (SE: 9.9). They had severe bronchial obstruction: mean FEV1 was <33% (10.6) of predicted values, with some CO2 retention: mean PaCO2 was 45.6 (7.1) mm Hg. By December 31, 1995, 189 patients had died (75%) and 13 (5%) were unavailable for follow-up. RESULTS: The overall crude survival was poor: 80.9% after 1 year, 67.1% after 2 years, 34.7% after 5 years, and 7.1% after 10 years. In the crude multivariate analysis (Cox), the negative prognostic factors were age and hypercapnia. The overall relative survival (Hakulinen), corrected for life expectancy, was 82.8% after 1 year, 70.8% after 2 years, 41.5% after 5 years, and 10.25% after 10 years. In the final multivariate relative model, age was no longer significant and the only bad prognostic factor was hypercapnia with a relative risk of 1.97 (1.16 to 3.34). CONCLUSION: This work shows the inadequacy of the Cox observed survival model when it comes to appreciating the real prognostic impact of age, because of the confusing factor associated with a normal life expectancy.
Authors: Fernando J Martinez; Gregory Foster; Jeffrey L Curtis; Gerard Criner; Gail Weinmann; Alfred Fishman; Malcolm M DeCamp; Joshua Benditt; Frank Sciurba; Barry Make; Zab Mohsenifar; Philip Diaz; Eric Hoffman; Robert Wise Journal: Am J Respir Crit Care Med Date: 2006-03-16 Impact factor: 21.405
Authors: Claudio Terzano; Fabio Di Stefano; Vittoria Conti; Marta Di Nicola; Gregorino Paone; Angelo Petroianni; Alberto Ricci Journal: PLoS One Date: 2012-04-23 Impact factor: 3.240
Authors: Thomas Blankenburg; Christin Benthin; Stefanie Pohl; Anett Bramer; Frank Kalbitz; Christine Lautenschläger; Wolfgang Schütte Journal: Open Respir Med J Date: 2017-06-30
Authors: Kristian Brat; Marek Plutinsky; Karel Hejduk; Michal Svoboda; Patrice Popelkova; Jaromir Zatloukal; Eva Volakova; Miroslava Fecaninova; Lucie Heribanova; Vladimir Koblizek Journal: Int J Chron Obstruct Pulmon Dis Date: 2018-03-26