Using forced vital capacity (FVC) in the clinic to monitor patients with idiopathic pulmonary fibrosis (IPF): pros and cons

Figures & data

Table 1. Summary of recommendations for quality assurance of spirometry [19]

Topic	Recommendations^a
Spirometer	Must meet current standards for accuracy, linearity, and repeatability Must provide both volume-time and flow-volume real-time displays If possible, use same spirometer for all measurements in an individual patient Ensure that software is up to date with current ATS/ERS guidelines
Calibration verification	Must be performed daily Inject 3-L calibration syringe ≥3 times to yield range of flows between 0.5 and 12 L/s If in-line filter is used in spirometry testing, then use filter during verifications Regularly inspect syringes for leaks or damage Volume of each injection must be within 3% of syringe volume Determine zero-flow level prior to all calibration verifications and patient tests Testing biological controls (healthy nonsmoking individuals) can be included but should not be considered a substitute for using the 3-L syringe
Technologist or operator	Must review data to confirm software decisions or alerts regarding acceptability and repeatability Must determine if further maneuvers are needed If possible, same technologist should perform all testing in an individual patient
Patient data	Any new illnesses or change in the patient’s condition should be noted, including comorbidities
Patient preparation	The patient should be provided with a list of activities to avoid and medications to withhold prior to testing Deviations from instructions must be recorded If possible, the same time of day should be used for follow-up and longitudinal testing
Test performance and acceptability and repeatability criteria	Follow current ATS/ERS recommendations for an acceptable FVC maneuver When a patient’s best effort does not meet acceptability criteria (e.g. due to coughing): The technologist should override the designation in the software and add a comment to the report The SVC maneuver may be a useful alternative, with the technologist coaching the patient to achieve maximal inspiratory and expiratory volumes with relatively constant flow After obtaining ≥ 3 acceptable FVC or SVC maneuvers: Difference between largest and second-largest FVC or SVC value should be < 0.150 L If repeatability criterion is not met: Additional maneuvers should be obtained The patient may require extra time to rest between maneuvers, due to exhaustion or increased dyspnea
Grading the quality of a test session	Grading should be provided to the interpreter to describe quality of test results The official 2019 ATS/ERS statement includes an example grading scheme for acceptability and repeatability For sessions with lower grades, the interpreter must use clinical judgment regarding an FVC value

ATS, American Thoracic Society; ERS, European Respiratory Society; FVC, forced vital capacity; SVC, slow vital capacity.

^aThis is a brief summary of international recommendations. For more information, clinicians should refer to the official ATS/ERS technical statement on the standardization of spirometry [19].

Table 2. Studies of home spirometry in patients with IPF and unclassifiable ILD

Reference	Study design	Patients, N^a	Study duration^b	Key home spirometry findings
Russell et al. [30]	Substudy of the multicenter, observational PROFILE study [34]	50	279 days (median)	Highly correlated with in-clinic assessments FVC decline was predictive of mortality
Johannson et al. [29]	Single-center, prospective, single-arm study	25	24 weeks	Enhanced precision and power with weekly assessments vs. only baseline and 6-month in-clinic assessments
Moor et al. [31]	Single-center, prospective, pilot study	10	4 weeks	Good agreement with in-clinic assessments
Swigris et al. [32]	Multicenter, prospective, observational study	50	6 months	Technical issues and insufficient data surveillance contributed to reduced adherence and missing data Patterns in home spirometry often did not agree with in-clinic trends
Maher et al. [33]	Multicenter, prospective, randomized, placebo-controlled trial	253	24 weeks	High intra individual variability prevented the application of the planned statistical model Differences in FVC decline between treatment groups were measurable at 6 months

FVC, forced vital capacity; ILD, interstitial lung disease; IPF, idiopathic pulmonary fibrosis.

^aAll studies enrolled patients with IPF, except for Maher et al., which enrolled patients with progressive fibrosing unclassifiable ILD. ^bThe listed study durations are as reported by the authors.

Figure 1. Distribution of absolute (a) and relative (b) changes in FVC (mL) over 3-month intervals in patients with IPF enrolled in randomized, controlled trials [5]. Histograms depict FVC changes over 3966 intervals of 3 months in 954 patients with IPF. The analysis population comprised 624 patients randomized to receive placebo in ASCEND (Study 016; NCT01366209) and CAPACITY (Studies 004 and 006; NCT00287716 and NCT00287729) and 330 patients randomized to receive interferon γ-1b or placebo in GIPF-001 (NCT00047645). FVC, forced vital capacity; IPF, idiopathic pulmonary fibrosis

Figure 2. Using FVC in the clinic to monitor patients with IPF: pros and cons. FVC, forced vital capacity; IPF, idiopathic pulmonary fibrosis

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