CT Scan Appearance, Densitometry, and Health Status in Protease Inhibitor SZ α1-Antitrypsin Deficiency

doi:10.1378/chest.09-0057

Chest

Volume 136, Issue 5, November 2009, Pages 1284-1290

https://doi.org/10.1378/chest.09-0057 Get rights and content

Background

The aim of this study was to uniquely describe CT scan appearance, densitometry, and health status in subjects with protease inhibitor SZ phenotype (PiSZ) α₁-antitrypsin deficiency (AATD) compared with matched subjects with protease inhibitor ZZ phenotype (PiZZ).

Methods

The presence and type of emphysema seen on CT scan, upper and lower zone densitometry, health status, physiology, and symptoms were compared for 126 subjects (63 with PiSZ, 63 with PiZZ) from the UK AATD registry, matched for age, gender, and smoking status. Similar analyses were performed for lung index and nonindex subgroups.

Results

A lower proportion of PiSZ index (46%) and non-PiSZ index (15%) subgroup case patients showed visible emphysema on CT scans compared with matched PiZZ index (91%; p < 0.001) and non-PiZZ index (61%; p = 0.011) case patients. Sixty-five percent of subjects with PiSZ and 74% with PiZZ had panacinar emphysema (p = 0.54); however, a greater proportion (p = 0.005) of the PiSZ group (39%) had upper zone-predominant emphysema compared with the PiZZ group (12%). Densitometric analysis revealed less extensive emphysema in the lower zones, but not the upper zones, of subjects with PiSZ than those with PiZZ. When subjects were matched for ascertainment method, health status was similar between the two phenotypes, despite the differences in CT scan and densitometry findings, and more abnormal respiratory physiology test results in subjects with PiZZ.

Conclusions

Subjects with PiSZ showed less emphysema on CT scans, more apical predominance, less abnormal respiratory physiology test results, but similar health status impairment compared with matched subjects with PiZZ.

Section snippets

Materials and Methods

AAT concentration (in micromoles per liter) was measured and the phenotype determined by isoelectric focusing (Heredilab; Salt Lake City, UT). Demographic data, the reason for testing for AATD, smoking history, and symptoms were recorded.

CT scans were acquired using a high-resolution protocol on the following two different scanners: GE Pro Speed Scanner (prior to March 2003) and GE Lightspeed Scanner (after March 2003) [General Electric Medical Systems; Milwaukee, WI]. Slices of 1 mm were

Demographic Data

More of the 63 subjects with PiSZ were identified by family screening (n = 19) than matched subjects with PiZZ (n = 8; p = 0.011). Three subjects with PiSZ and two subjects with PiZZ received their diagnosis due to abnormal serum electrophoresis findings during an investigation for unrelated symptoms. The reason for diagnosis is unknown for one subject with PiSZ and for two subjects with PiZZ (Table 1).

The mean AAT level was 13.2 ± 3.0 μmol/L for the subjects with PiSZ and < 11 μmol/L in 13 of

Discussion

We have reported unique CT scan appearance, densitometric analysis, and health status for 63 subjects with PiSZ and AATD. Emphysema was visible on CT scans in only 46% of the subjects in the PiSZ index subgroup, and in 15% in the nonindex subgroup. More subjects with PiSZ than those with PiZZ had apical predominant emphysema, as opposed to the classic basal distribution. Despite these findings, the majority of subjects with PiSZ or PiZZ had panacinar emphysema, which is more commonly associated

Acknowledgments

Author contributions: Dr. Holme was involved in data collection, undertook all statistical analyses, and wrote the manuscript. Dr. Stockley procured funding, supervised the work, reviewed the analysis, and edited the manuscript.

Financial/nonfinancial disclosures: Dr. Holme received funding to attend international conferences from Altana Pharma, payment for assisting in the organization of an educational event from AstraZeneca, and lecture fees from AstraZeneca and GSK. Dr. Stockley has received

References (0)

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Funding/Support: This research was supported by an unrestricted grant from Talecris Biotherapeutics, Research Triangle Park, NC.

This study was performed at the University Hospital Birmingham NHS Foundation Trust, Birmingham, UK.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/site/misc/reprints.xhtml).

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