Table 2.

Current (Pre-COVID-19) Guidelines for the Evaluation of Subsolid Lung Nodules

CHEST4	The Fleischner Society5	Lung-RADS7	BTS6
< 6 mm GG: No routine follow-up	< 6 mm GG: No routine follow-up PS: No routine follow-up Multiple: CT scan at 3-6 mo, consider CT at 2 and 4 y if stable	GG: < 30 mm or any size and unchanged: RTAS (category 2) PS: < 6 mm: baseline RTAS (category 2), new 6-mo CT (category 3)	< 5 mm: No follow-up
≥ 6 mm GG: 12 mo then annual through 3 y PS: ≤ 8 mm solid, 3, 12, and 24 mo, then annual mo, then annual until 5 y; > 8 mm solid, 3 mo, further evaluation if persists	≥ 6 mm GG: 6-12 mo then every 2 y until 5 y PS: 3-6 mo then annual until 5 y Multiple: 3-6 mo then based on most suspicious nodule	GG: > 30 mm or new: 6-mo CT scan (category 3) PS: solid component < 6 mm, 6-mo CT (category 3); solid component ≥ 6-8 mm or new or growing and < 4 mm, 3-mo CT (category 4A); solid component ≥ 8 mm or new or growing and ≥ 4 mm, further evaluation (category 4B)	≥ 5 mm: 3-mo CT growth or altered morphology favors resection, stable, use Brock model, < 10% then CT scan at 1, 2, and 4 y from baseline, > 10% or concerning morphology, surveillance, biopsy, or resection

GG = ground-glass; PS = part-solid. See Table 1 legend for expansion of other abbreviations.