Proportion of sequence reads removed from adenoid swab compared to adenoid biopsy. (A) Proportion of reads removed by pre-filtering human OTUs in adenoid swab (n = 11) and adenoid biopsies (n = 11). ***P < 0.002, Mann–Whitney test. (B) Relative abundance of sequences identified as artefact in adenoid swab and adenoid biopsies. *P < 0.032, Mann–Whitney test.