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Joint Fluid Cytology for Crystals

Cellular Pathology

Principle of Examination:

The majority of joint fluids and synovial fluids are sent to the cytology department for crystal investigation – specifically gout and pseudogout.

  • Gout describes a group of metabolic disorders where crystals of monosodium urate (uric acid) deposit in the tissues.
  • Pseudogout is an acute, inflammatory form of arthritis. Like gout, pseudogout involves the deposit of crystals, in this case calcium pyrophosphate, in and around the joint tissues.
  • Septic Arthritis: In some cases where crystals are not present there may be large numbers of inflammatory cells, in this case the diagnosis may be suspicious of septic arthritis, otherwise known as bacterial arthritis. The patient benefits from a rapid diagnosis and treatment of this condition because joints may deteriorate in a short period of time. In these cases, therefore, microbiological culture would be a more appropriate test.

Specimen Requirements

When sending a joint fluid aspirate for Cytology:

  • To ensure best results, we request that as much fresh specimen be sent to the laboratory as possible, within 24hrs of collection.  Fresh or unfixed specimens must be received on the same day as collection.
  • Use a 30ml Sterilin universal container. We regret that we are unable to accept specimens in drainage bags or leaking containers.
  • Aspirated fluid should be sent fresh or with an added anticoagulant – such as Lithium Heparin.(NB: Do NOT use crystalline anticoagulants or chelating anticoagulants)
  • There should be adequate clinical information provided on the request form, which should clarify the indication for a cytological examination.
  • Send a separate specimen and request form for microbiological investigation if an infection is suspected and a culture and sensitivity is required.

Specimen Delivery and Labelling

All Trust specimens must be requested on Epic and labelled with an Epic label.

Specimens from outside of the Trust should be accompanied by a fully completed request form or a GPOCS request.

The request should state:

  • Three patient identifiers
  • Specimen type i.e. ‘joint fluid for crystal analysis’
  • Source of specimen i.e. ‘left knee’, ‘right wrist’
  • Date and time of sample collection
  • Requesting clinician
  • Patient location – inpatient/outpatient/ward/GP surgery

HIGH RISK SPECIMENS: The request (electronic or paper) must indicate if a specimen is high risk.  Please indicate details of the risk, eg: Covid, TB, blood-borne virus, etc.

URGENT SPECIMENS: Please label urgent specimens clearly; an explanation as to why the specimen is urgent is helpful. On receipt, laboratory staff will notify the pathologist who will report the specimen as soon as possible.

Turnaround Time

The Laboratory aims to comply with The Royal College of Pathologists Key Performance Indicator (KPI 6.4) for Cellular Pathology reporting turnaround times with 90% of all cases reported within 10 calendar days.



Specimen Labelling Procedure
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