The importance of plasma screening
8 Apr 2010 by Evoluted New Media
The haematology department at Musgrove Park Hospital have just bought their plasma viscosity equipment up-to-date – we get an insight in to why plasma screening is important
The haematology department at Musgrove Park Hospital have just bought their plasma viscosity equipment up-to-date – we get an insight in to why plasma screening is important
MUSGROVE Park Hospital is the largest general hospital in Somerset and is the birthplace of the Plasma Viscometer. It is from this hospital that Professor Jock Harkness developed the Harkness Viscometer first introduced in 1971, sparking a long history of plasma viscosity (PV) testing by the Somerset Pathology Service.
Plasma viscometers are used for monitoring Multiple Myeloma (MM) and Waldenstrom’s Macroglobulinaemia (WM). They work by drawing a small sample of plasma through a narrow capillary using a constant pressure and measuring the time taken for the sample to move a known distance. Results can be grouped into broad bands to give an indication of the underlying condition.
Many laboratories use a combination of ESR (Erythrocyte Sedimentation), CRP and PV testing; the Somerset Pathology Service – a joint venture between Musgrove Park and Yeovil District Hospital – is very specific about the diagnostic capabilities of using plasma.
“The ESR and CRP are not the same as PV but they provide us with non-specific screening tools for suspected infection and inflammation to assist the clinician in making a diagnosis alongside the patients’ clinical signs and symptoms,” said Graham Gibbs, Haematology technical manager at Musgrove Park.
“A high ESR or CRP could be due to many things. However, if we get a PV result over 3mPas we are moving into the diagnostic arena. It is no longer non-specific as very few conditions are associated with values as high as this. Multiple Myeloma and Waldenstrom’s Macroglobulinaemia are top-of-the–list and trigger other confirmatory tests such as protein electrophoresis and serum free light chain and immunoglobulin testing,” he continued.
Gibbs says that once a diagnosis has been made, the PV test can be used to help monitor patient treatment and progress. “Occasionally, the GP will send in a full blood count (FBC) with low haemoglobin and this will trigger a blood film. Sometimes the slide stains bright blue telling us that there is a lot of protein present in the blood. The film examination reveals the red blood cells stacked up like piles of coins – this is called rouleaux and is another indication of raised plasma proteins. We then do a PV test and this is often the way that new MM and WM patients are first discovered.”
In the 1990’s, PV testing was very much a part of the busy routine service and was processing 250 viscosities daily. However, the withdrawal of a market-leading viscometer in 1997, combined with staff shortages meant the laboratory had to rethink its service delivery model – it was just no longer feasible to continue to process such large numbers of PV requests.
With automated systems for ESR and CRP testing, the laboratory chose to use a PV system suitable for scaled down testing. “We like to use the PVs for monitoring Multiple Myeloma and Waldenstrom’s Macroglobulinaemia but the routine viscosity haematology screen was abandoned, we did not have the manpower or the technology and we did not have the machine,” Gibbs said.
“At the time that we were looking for a replacement PV system, funding was not available to go to the larger Benson system so we chose to use another supplier for our PVs. The principle was nice, it appeared to be low maintenance but it had unforeseen technical problems,” he continued, “With the replacement system we had to use cold packs and a fan before we could get a result out – it was a joke.”
Continuing system issues and a shrinking network of users was forcing Musgrove Park to consider stopping the service altogether. “We were close to shutting down all PV testing and shipping our samples to Exeter. It would have been a great shame and the end of an era for us. It’s a useful tool and we would have been very upset to lose it,” Gibbs said, “The Benson BV1 appeared just at the right time and so we were a lot more interested in continuing the service.”
The BV1 was commissioned in February 2009. The laboratory was attracted by the concept of a one-shot system – with only half a dozen PVs per week for MM and WM patients it meant the lab would be processing around one test a day.
“Benson Viscometers has a fine reputation for quality and they are held in high regard by users,” Gibbs said, “The BV1 is superbly engineered and easy to use, it’s painless and we like it. We liked the appearance, it is innovative using a modified PC cabinet and we liked the small footprint. Customer support is second to none.”
“We may never go back to 250 per day, we don’t have the staff but PV measurement is still an important part of our haematology service and the consultant haematologists order them when appropriate,” Gibbs said.
The arrival of the BV1 has ensured the future of PV testing at Musgrove Park. Gibbs and his staff are delighted with their new viscometer and its contribution towards high quality patient care in Somerset.
