# Test the smallest safe discard volume for blood taken from ports and PICCs in cancer outpatients

Source: https://onco.cc/ideas/idea-upgrade-central-line-discard-volume-in-cancer-outpatients/  
OnCo record `idea-upgrade-central-line-discard-volume-in-cancer-outpatients` (Idea). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

When blood is taken from a line, a small amount is usually drawn off and thrown away first. How much is needed has never been set by a guideline that could be read, and the only recent study was in intensive care, not in people with ports having chemotherapy.

## Summary

The gap. No guideline read for the blood sampling protocol sets a discard volume; the INS Standards, which do, could not be read. An intensive-care study in 105 patients found a 2 ml discard gave results agreeing with venepuncture for electrolytes and blood counts except white cells (abstract), and noted that no consensus exists on the volume. People with cancer have bloods taken from their lines before nearly every cycle.

## Fields

- Kind: Idea
- Last checked: 2026-11-11
- Tags: protocol-upgrade; upgrade:untested; evidence:insufficient
- Hypothesis: In outpatients sampled from implanted ports and PICCs after a saline lock, a discard of a set small volume gives blood counts and biochemistry that agree with venepuncture within clinically acceptable limits.
- Rationale: A volume that is too small gives diluted results that can wrongly delay chemotherapy; one that is too large wastes blood in people who are often anaemic.
- Proposed test: A paired-sample method-comparison study in chemotherapy day units: venepuncture against line samples after discards of increasing volume, stratified by device, with Bland-Altman agreement for haemoglobin, neutrophils, platelets, creatinine and potassium.
- Maturity: early-clinical
- Actor: clinic

## Sources

- Pushparaj et al., Minimizing discard volume to 2 ml before blood sampling from a central venous catheter (Acute Crit Care 2026; abstract read): https://doi.org/10.4266/acc.000792

## Connected records

- fronts: [Chemotherapy](https://onco.cc/fronts/chemotherapy/), [Supportive Care & Survivorship](https://onco.cc/fronts/supportive-care/)
- technologies: [Implanted ports for chemotherapy (port-a-cath, power-injectable, apheresis and intraperitoneal ports)](https://onco.cc/technologies/implanted-ports/), [Peripherally inserted central catheters (PICC lines)](https://onco.cc/technologies/picc-lines/)
- terms: [Central venous access (port, PICC line)](https://onco.cc/terms/central-venous-access/)
- bottlenecks: [Toxicity and quality of life are undervalued](https://onco.cc/bottlenecks/b-toxicity-qol/)
- ideas: [Masks on patient and nurse, and the head turned away, while a port is accessed: a comparison of infection rates](https://onco.cc/ideas/idea-upgrade-masks-and-head-turn-at-port-access-infection-study/)
- protocols: [Blood sampling from a central line or port](https://onco.cc/protocols/blood-sampling-from-a-central-line/)

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