Overview: Percentage Positive Cells TestIntroduction: The Percentage Positive Cells Test measures the percentage of positive cells in tissue to assess cancer severity or treatment response, helping guide cancer therapy. Affecting 1 in 100 people with cancer, cell positivity poses diagnostic challenges due to tumor variability. Following 2023 National Comprehensive Cancer Network (NCCN) guidelines, it uses immunohistochemistry for high accuracy, supporting histopathology screening. This test is vital for diagnosis, treatment planning, and improving outcomes in oncology.
Other Names: Cell Positivity Test, Cancer Marker Assay.
FDA Status: Laboratory-developed test (LDT), meeting histopathology standards for diagnostic reliability.
Historical Milestone: Cell positivity testing began in the 1980s with research by Gerdes, who developed Ki-67 methods. Immunohistochemistry advancements in the 1990s by Dako improved detection, surpassing earlier manual counts.
Purpose: Measures percentage of positive cells to assess cancer severity, guides chemotherapy or immunotherapy, and evaluates patients with cancer history, aiming to manage disease.
Test Parameters: Percentage of positive cells
Pretest Condition: Tissue biopsy required. Collect tissue or whole blood. Report history of cancer.
Specimen: Tissue (FFPE, 0.5-2 cma³), Whole Blood (EDTA, 2-5 mL); Tissue in sterile container. Transport in a biohazard container.
Sample Stability at Room Temperature: 24 hours
Sample Stability at Refrigeration: 48 hours
Sample Stability at Frozen: 1 month
Medical History: Document cancer history or abnormal growth. Include current medications or family history.
Consent: Written consent required, detailing the test's purpose, disease risks (e.g., metastasis), and sample collection risks.
Procedural Considerations: Uses immunohistochemistry to measure positivity, requiring labs with staining facilities. Results available in 3-5 days. Performed in labs with strict handling.
Factors Affecting Result Accuracy: Sample degradation or contamination can affect results. Medications may not affect results but require correlation.
Clinical Significance: High percentage suggests aggressive cancer, guiding therapy. Early treatment might improve survival, while untreated cases lead to progression. Normal levels may require other tests.
Specialist Consultation: Consult an oncologist for interpretation.
Additional Supporting Tests: Biopsy, CT scan, or PDL1 test to confirm diagnosis.
Test Limitations: Non-specific for cancer type; correlation with imaging needed. False negatives possible with low positivity.
References: NCCN Guidelines, 2023; Cancer Research, Gerdes J, 2022.
