How to Write a Laboratory SOP That Meets NABL Standards

Standard Operating Procedures (SOPs) are the backbone of a NABL-accredited laboratory’s quality system. A poorly written SOP is worse than no SOP — it creates confusion and invites non-conformances.

ISO 15189:2022 requires that all processes affecting quality be documented and followed consistently. SOPs are the primary mechanism for achieving this. Here’s how to write SOPs that pass NABL scrutiny and genuinely work in practice.

Essential Elements of a NABL-Compliant SOP

1. Document header: Document number, title, version, effective date, department, pages
2. Purpose: Why does this SOP exist? What problem does it solve?
3. Scope: Which activities and personnel does this SOP apply to?
4. Responsibility: Who performs and who supervises this procedure?
5. Abbreviations/Definitions: Explain any technical terms
6. Materials and equipment required: What you need before starting
7. Procedure: Step-by-step instructions in clear, imperative language
8. Reference values/acceptance criteria: How do you know the procedure succeeded?
9. Quality control: QC steps integrated into the procedure
10. Safety precautions: PPE, hazards, waste disposal
11. References: Source documents (manufacturer manual, textbooks, standards)
12. Revision history: All previous versions with reason for change
13. Approval signatures: Author, technical reviewer, Quality Manager, Lab Director

Common SOP Writing Mistakes

• Too generic — not specific to your lab’s equipment and reagents
• Not updated when equipment or methods change
• Written by one person and never reviewed by someone who actually performs the procedure
• No IQC section in analytical SOPs
• Approval signatures missing or outdated