| Supported Specimen Types | Cerebrospinal fluid, plasma, serum, and validated research matrices with matrix-specific performance data. | One or two commonly used matrices supported by published or internally documented validation. | Results may not be comparable when the assay has not been validated for the requested matrix. | Can you provide validation data for the exact specimen type, anticoagulant, and concentration range? |
| Sample Collection and Stabilization | Documented collection tubes, processing time, centrifugation conditions, aliquot volume, and storage temperature. | Basic instructions for collection, separation, freezing, and shipment. | Uncontrolled pre-analytical variation can affect biomarker concentration before testing begins. | What is the maximum permitted time from collection to processing, and how many freeze-thaw cycles are allowed? |
| Shipment and Chain of Custody | Temperature-monitored shipment, tamper-evident documentation, sample receipt checks, and deviation reporting. | Insulated shipment with dry ice or validated cold packs and basic receipt confirmation. | Temperature excursions or missing sample history may compromise data interpretation. | Do you record transit temperature, receipt condition, and any deviations before analysis? |
| Testing Method | A fit-for-purpose method such as validated immunoassay, electrochemiluminescence, or targeted mass spectrometry, selected according to the analyte. | Established immunoassay with documented analytical performance for the intended research use. | Different platforms may produce non-interchangeable results because of calibration, antibody specificity, or peptide coverage. | Which analytical platform is used, and has method comparison been performed against an independent reference method? |
| Analytes and Biomarker Panel | Clearly defined targets, including amyloid-beta ratios, phosphorylated tau species, total tau, and optional neurodegeneration markers where relevant. | A focused panel covering the main research question and available specimen type. | Similar analyte names may represent different molecular forms, epitopes, or reporting conventions. | Are the exact molecular targets, epitopes, isoforms, and calculation formulas specified in the technical documentation? |
| Analytical Sensitivity | Limit of detection and lower limit of quantification established using the intended matrix, with low-end precision data. | Sensitivity reported from assay validation, but with limited matrix-specific information. | Values near the detection limit may have higher imprecision and should not be over-interpreted. | What are the detection and quantification limits in the exact sample matrix? |
| Precision and Reproducibility | Intra-assay and inter-assay precision reported across low, medium, and high concentration controls, with coefficients of variation. | Repeatability tested with routine quality-control samples. | A single repeat measurement does not establish long-term reproducibility. | What precision data are available across different days, operators, reagent lots, and instrument runs? |
| Accuracy and Calibration | Traceable or well-characterized calibrators, documented calibration model, recovery studies, dilutional linearity, and spike-recovery data. | Routine calibration with basic recovery and linearity checks. | Results from different assay lots or laboratories may shift if calibration is not harmonized. | How are calibrators assigned, and what evidence supports accuracy in the requested matrix? |
| Interference and Specificity | Interference assessed for hemolysis, lipemia, icterus, biotin where relevant, heterophile antibodies, and structurally related proteins. | Common interference risks listed in the assay documentation. | Interfering substances can cause falsely elevated or reduced measurements. | Which interference studies were performed, and what rejection or flagging criteria are applied? |
| Quality-Control Program | Multi-level controls, run acceptance rules, duplicate testing where appropriate, lot-to-lot checks, and documented corrective actions. | Internal controls included in each analytical batch or according to a documented schedule. | Poorly defined acceptance rules can allow drift or batch effects to remain undetected. | Can you provide the quality-control levels, acceptance ranges, and batch rejection criteria? |
| Data Reporting | Raw and processed results, units, reference ranges or decision thresholds, dilution factors, flags, missing-value codes, and assay metadata. | Processed concentration results with basic quality flags and units. | Incomplete metadata makes it difficult to reproduce analyses or compare cohorts. | Will the final dataset include sample identifiers, run identifiers, batch information, units, and quality flags? |
| Data Integrity and Security | Controlled access, audit trails, version-controlled files, documented data corrections, and secure transfer procedures. | Password-protected data delivery with basic file versioning. | Untracked edits or inconsistent file versions can undermine study traceability. | How are data changes, access permissions, and final-file approval documented? |
| External Evidence and Comparability | Independent publications, proficiency testing or inter-laboratory comparison, and clear explanation of cross-platform limitations. | Internal validation report and relevant technical references. | Published performance may not transfer directly to a different cohort, matrix, or pre-analytical workflow. | What independent evidence supports performance in a population and workflow similar to ours? |
| Overall Selection Priority | Choose the option with the strongest matrix-specific validation, transparent QC, complete metadata, and reproducible sample logistics. | Use a lower-evidence option only when limitations are documented and addressed in the study design. | Lowest price or broadest panel alone does not demonstrate analytical or clinical validity. | Can the supplier provide a complete method-validation package before the purchase or study start? |