Key Point

CT may detect bronchiolitis in lung transplant recipients earlier than lung function tests.

VANCOUVER, BRITISH COLUMBIAS—Currently, there is growing interest in the use of CT to detect bronchiolitis obliterans in patients who have undergone lung transplantation. Because CT can directly evaluate various anatomic markers of transplant dysfunction, experts believe that it may permit detection of bronchiolitis at an earlier stage than with lung function tests.

A study by de Jong and colleagues has confirmed this hypothesis by showing that CT-based air-trapping and composite bronchiolitis scores were significantly associated with FEV1 among 38 single- or double-lung transplant recipients.¹ In addition, both scores predicted the clinical course of the patients over the year following CT evaluation, and intraobserver and interobserver agreement for the two scores was generally good (ie, at least 0.8).

Each patient’s scores were based on the first CT scan completed after lung transplantation (baseline scan) and on the first annual follow-up scan. Two investigators randomly scored the scans on a scale of 0 to 100 for the extent of bronchiectasis, mucous plugging, airway wall thickening, consolidation, mosaic pattern, and air trapping. Results for all of those variables were combined into the composite bronchiolitis score.

The mean interval between lung transplantation and baseline CT was 44 months, and the interval between baseline and follow-up CT was 11.2 months.

Intraobserver and interobserver agreement for the air-trapping score was 0.97 and 0.86, respectively. For the composite bronchiolitis score, intraobserver agreement was 0.94; but at 0.78, interobserver agreement was borderline. Increases in both scores corresponded with declines in FEV1.

A 1% rise in the baseline composite bronchiolitis score predicted a 1.25% more rapid worsening of that score and a 1.55% increase in the rate of FEV1 decline during the following year. A 1% rise in the baseline air-trapping score accelerated worsening of FEV1 and composite bronchiolitis score by 0.27% and 0.74%, respectively, during the following year. These findings suggest that the composite bronchiolitis and air-trapping scores could identify bronchiolitis earlier in lung transplant recipients than FEV1 measurements could, the investigators pointed out.

Thus, CT may be a valuable tool in the evaluation and follow-up of these patients. "Lung function is currently the ‘gold standard’ for detecting lung allograft dysfunction, but is only an indirect measurement and can only give a global assessment of pulmonary condition," the investigators pointed out.

FAILED LUNG TRANSPLANTS SHOW VARIED HISTOLOGY

Having to perform lung retransplantation because of bronchiolitis is never desirable, but it does offer a rare chance to look at the old graft to see what went wrong. Martinu and colleagues had that chance a dozen times from 1992 to 2004, and their findings were especially surprising with regard to fibrotic changes.²

"Patients with moderate or mild fibrosis often exhibited more severe epithelial and inflammatory changes, possibly contributing to the clinical severity of their [bronchiolitis obliterans syndrome]" said the investigators. "All allografts demonstrated some histologic evidence of acute rejection."

Histologic findings other than bronchiolitis included superimposed infectious bronchitis, chronic bronchitis, multifocal organizing pneumonia, arteriopathy, extensive interstitial fibrosis, and focal emphysema, invasive aspergillosis, and interstitial fibrosis. "Cholesterol clefts were seen in four patient allografts, with one of these patients also demonstrating lipoid pneumonia," the investigators added.

Among the 11 patients who had chest CT before they underwent retransplantation, only three demonstrated changes that were suggestive of bronchiolitis. These changes included ground-glass opacities with intralobular thickening, traction bronchiectasis, areas of fibrosis, and pleural thickening.

The investigators’ conclusion: "[S]ignificant histologic heterogeneity exists among patients undergoing retransplantation for [bronchiolitis obliterans syndrome] potentially contributing to the variability of patient responses to treatment."

—Timothy Begany

Reference
1. de Jong PA, Dodd JD, Coxson HO, et al. Bronchiolitis obliterans following lung transplantation: early detection using CT. Thorax. 2006 May 2; [Epub ahead of print].
2. Martinu T, Howell DN, Davis RD, et al. Pathologic correlates of bronchiolitis obliterans syndrome in pulmonary retransplant recipients. Chest. 2006;129:1016-1023.

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