Extent of Lung Fibrosis on HRCT

There were 11 deaths (42%) in the fibrotic group and 1 death (2%) in the nonfibrotic group during the median follow-up period of 5.8 years (Fig 1). In the regression analysis, the presence of HRCT fibrosis, more severe impairment of pulmonary function parameters, and presence of crackles on auscultation were predictive of reduced survival (p < 0.05 for all) [Table 2]. The age-adjusted hazard ratio for mortality in patients with HRCT fibrosis was 4.6 (95% confidence interval, 2.0 to 20.1; p < 0.0001). The presence of honeycombing in itself was not predictive of mortality (only five patients had honeycombing).

Lung Fibrosis

Figure 3 demonstrates the relationship between the fibrosis extent and mortality. Mortality was highest in patients with > 40% of lung involvement (5 of 6 patients died, 83%), followed by those with 10 to 40% involvement (3 of 6 patients died, 50%), followed by those with < 10% involvement (3 of 14 patients died, 21%) and those with no lung fibrosis (1 of 43 patients died, 2%).

Extent of Lung Fibrosis on HRCT

Figure 3. Relationship between the fibrosis extent and mortality. The presence of fibrosis was assessed semiquantitatively as absent or as involving < 10%, 10 to 40%, or > 40% of the lung. The numbers in the bar graph refer to the fraction of deceased patients in each category (nominator) over the number of all patients in that category (denominator).

Discussion

Our study found radiologic evidence of parenchymal fibrosis to be associated with decreased survival in patients with HP. Furthermore, the extent of parenchymal fibrosis, as assessed by semiquantitative visual scoring of CT, correlated with mortality.

HP may lead to progressive clinical deterioration and death in a proportion of patients. Mortality in our study was 17%, comparable to reports from other tertiary care referral medical centers. The long-term mortality estimates in chronic HP are reported as low as 1% in the community study, of patients with farmers’ lung, and as high as 27% in the population of patients from tertiary referral medical centers. A large-scale epidemiologic study from England suggests that all-cause mortality is three times higher in patients with HP compared to the general population.

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