A grading scale can be used to assess the consistency of patient blows. Spirometry results are best interpreted when breathing maneuvers are done with maximal lung volume and maximal effort as these are easily repeatable. The American Thoracic Society recommends the grading system below for spirometry interpretation, which includes children as well. The repeatability grade is used to assess a set of prebronchodilator and post-bronchodilator maneuvers separately, rather than individual maneuvers. Differences between the 2 largest FEV1 and 2 largest FVC values are compared for the repeatability criteria. Grade U was included to indicate that usable but not acceptable values were obtained.
Although some patients maybe not meet the requirements for a grade A, the results are still clinically useful. The providers' clinical judgement is important for interpreting the specific patients' results. Moreover, it is important to inform the patient that the grade assigned to their values are not an indication of the health of their lungs. Providers should inform patients that the grades represent consistency of their blows.
More details at: https://www.atsjournals.org/doi/full/10.1164/rccm.201908-1590ST