Readiness Level of Spanish Labs to Detect Mpox Clade Ib: A Nationwide EQA

To assess the preparedness and diagnostic capacity of Spanish clinical microbiology laboratories to detect the emerging monkeypox virus (MPXV) Clade Ib through a nationwide external quality assessment. A blinded 16-sample panel (serum and DNA eluates) containing MPXV Clade Ib, Clade II, vaccinia, and negatives was distributed. Of 36 laboratories submitting results, 25 with clade-level capability were included. Performance versus reference was adjudicated as full, partial, or discordant concordance; species-level and clade-specific metrics were estimated, and inter-laboratory agreement summarized with simple and weighted kappa (Wilson 95% CIs; bootstrap for kappa CIs). Species-level MPXV detection was consistently strong (mean sensitivity 85%, specificity 95%). Agreement was substantial (simple kappa 0.70; weighted 0.81). For Clade Ib, mean sensitivity was 50% (range: 0%-100%) with high but variable specificity (100%). For clade II, mean sensitivity averaged 70% (25%-100%) and specificity 98% (66.7%-100%). Methodologies varied across centers: 68% used independent extraction plus commercial PCR, 20% mixed commercial extraction with in-house PCR, and 12% integrated extraction-PCR platforms. In conclusion, Spanish laboratories maintain good capacity for MPXV species-level detection, but clade discrimination-particularly for emerging Clade Ib-remains heterogeneous and suboptimal across participating centers. Expanding QC panels to include new clades and updating/validating assays should enhance national readiness for future transmission events.