The main focus of this computational modelling study is to determine the extensional rheological response of sputum biofluids to provide a diagnostic tool (biomarker) for experimentally-based pathological analyses and clinical practice. This may be accomplished through advanced rheological parameterisation and characterisation of sputum samples, when considering extensional deformation flow situations that mimic sputum escalator deformation in the lung-airways. Sputum samples have been collected from patients (male and female, over fifty years of age) suffering from Chronic Obstructive Pulmonary Disease (COPD) at two stages of development: uninfected (stable or non-infective) state and infected (suffering exacerbations) state. Samples have been tested without any pre-treatment such as mechanical homogenisation. Experimental and numerical studies of Capillary Break-up Extensional Rheometer (CaBER) have been performed, from which comparison significant correlations are presented. Typically, the dynamic development of the mid-filament diameter is monitored during the process of necking and filament-failure (break-up). The aim is to link this type of data with that emerging from experimental/clinical trials to provide a biomarker revealing insight on state of disorder and resultant treatment. The rheology of sputum samples is represented through two rheological fluid modelling approaches: (i) a kinetic Single Extended porn-porn (SXPP) model and (ii) a time-dependent thixotropic Modified Bautista-Manero (MBM) model. These models are sufficiently rich to enable description of both network-structure and rheological properties, exhibiting viscoelastic response (memory), with strain-hardening/softening and shear-thinning properties. (C) 2015 Elsevier B.V. All rights reserved.