ATS Pulmonary Function Laboratory Manual

CHAPTER  12

REVIEW OF TEST RESULTS 1. Assure acceptable and repeatable spirometry data at pre-challenge and post-diluent stages. 2. Assure an acceptable maneuver at each time point of each stage. 2.1. Repeatability of FEV 1

(i.e., two highest within 0.150 L) may be difficult to obtain once methacholine

is administered.

3.

Assure FEV 1

is less than or equal to 80% of post-diluent FEV 1

value for a positive test.

4. Assure bronchodilator has been administered (if applicable) and post-bronchodilator spirometry per- formed, and FEV 1 is at least 90% of baseline.

REPORTING OF TEST RESULTS 1.

Data should be expressed as a percent decrease in FEV 1

from the post-diluent value (or pre-challenge value

if a diluent step is not used) in relationship to the calculated final dose. 2. If more than one diluent stage is used, the percent change is calculated from the final post-diluent stage. 3. Data should be presented for each step in the protocol, including post-bronchodilator spirometry. 4. For spirometry, report the FEV 1 , and FVC and FEV 1 /FVC ratio (if complete FVC maneuvers were per- formed). Also include: bronchodilator administered and dose, display of best flow–volume and/or volume– time curve from each step, PD 20 , or include a dose–response curve, and signs and symptoms after final dose. 5. For plethysmography measurements, report sGaw or specific resistance (sRaw). 6. Express the concentration as mg/ml and dose as cumulative dose units of methacholine (CUM). 7. Cumulative dose units 7.1. Methacholine has been shown to accumulate between concentrations because it is metabolized somewhat slowly (27). 8. Graphic and tabular displays showing percent change and absolute values should be presented in the report. 9. Technician comments should include evaluations of patient effort and cooperation, whether coughing oc- curred, and patient response to specific queries concerning the presence of shortness of breath, wheezing, and other symptoms that can be used to confirm the response. 10. If FEV 1 does not fall by at least 20% following the highest dose, then PD 20 should be reported as “greater than final dose given.” If FEV 1 falls by >20% following inhalation of diluent, a PD 20 is not reported. Instead, state, “there was a significant decrease in lung function following inhalation of the diluent and methacholine was not given.”

PROCEDURE NOTES 1.

Shortening the test procedure 1.1.

Doubling concentrations are recommended for research protocols and are mathematically attractive. However, the use of doubling concentrations requires more steps and increases the time for the test. Fewer concentrations have been used by investigators in order to save time without any apparent in- crease in risk or severe bronchospasm (28, 29). Quadrupling increments is recommended for clinical testing, but if the test is used to determine changes in airway reactivity following therapy in patients known to have asthma, using doubling doses will give more precise PD 20 values. The quadrupling dose schedule will result in a lower cumulative dose, but since the increase in dose is logarithmic, only the last one or two concentrations has a major effect on the PD 20 s.

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