RESUMO
BACKGROUND: In general, internal/external quality control of special stains for diagnosis of hematological diseases may be unavailable in a clinical laboratory owing to the lack of an appropriate positive/negative control material. METHODS: We developed a protocol on positive/negative control materials for five special stains (iron, myeloperoxidase [MPO], periodic acid-Schiff [PAS], Sudan black B [SBB], and alpha-naphthyl acetate esterase [ANAE]) using a hematological malignant cell line. First, we compared stainability of seven cell lines (HL-60, THP-1, K562, Kasumi-1, KG-1, KO52, and NKM-1), then confirmed duration of stable stainability. A proficiency test using external quality control materials was conducted at eleven institutions, which participated voluntarily. RESULTS: HL-60 and THP-1 cell lines, which showed good stainability among the seven cancer cell lines, were selected as external quality control materials. The stainability of a prepared cell line fixed on control slides was stable for 3–4 weeks (MPO, SBB, and PAS) or 9–10 weeks (ANAE). The stainability of paraffin-embedded control material for iron stain was stable for 3 months. The results from 11 institutions were the same on iron, MPO, SBB, and ANAE. Nevertheless, two of 10 institutes showed discrepant results on PAS. CONCLUSIONS: In this study, we demonstrated that cell lines could serve as a standard quality control material for special stains. Most institutions showed representative results on special stains except for PAS. This protocol for special stain may be useful as an external or internal quality control in a haematology laboratory.