By Gary N. Wolfe

StatSpin Express II STAT centrifuge saves crucial sample preparation time, boosting process efficiencies
Whether the locale is an emergency department, an operating room, a critical care unit, a clinic, or a central laboratory, the elapsed time to perform diagnostic tests is more critical than ever before. In the case of many, if not most, new test procedures and analytical systems entering mainstream usage, a key design criteria has been to reduce turnaround times (TATs) from hours to minutes or even seconds - all with the objective of speeding diagnoses so that the most appropriate patient care can be delivered as quickly as possible.

StatSpin’s Express 2 centrifuge

One of the ironies of this evolution in high-speed diagnostics is that ancillary procedures, such as sample preparation by centrifugation, which were far less time-critical in the era when diagnostic tests took hours or days to perform, are now often the most significant barriers to obtaining timely results. Clearly, when a test takes only 3-5 minutes, a 15- to 20-minute (or longer) sample processing time is troublesome. Alleviating such bottlenecks is the underlying rationale for developing the StatSpin Express 2 Primary Tube Centrifuge, available from StatSpin, a Norwood, Mass. based subsidiary of International Remote Imaging Systems, Inc., also the parent of Iris Diagnostics and ADIR Advanced Digital Imaging Research.

Reduced TAT is vital in POC settings
Current guidelines established by the American College of Cardiology, the American Heart Association, and the European Society of Clinical Cardiology recommend that the initial evaluation of patients with chest pain be performed within 20 minutes of their arrival in the emergency room. However, one of the key challenges today in the ED environment is the time-consuming process of transporting blood to a central laboratory and subsequently clotting and spinning down the sample in a conventional batch centrifuge. “All of these factors can add as much as 40 minutes to the turnaround time,” according to Bob Mello, corporate vice president of International Remote Imaging Systems and president of the StatSpin subsidiary.

Additionally, the guidelines say that the optimum TAT from patient arrival to the availability of the test results for these cardiac markers is 30 minutes or less. “So,” says Mello, “it’s not unusual for some central labs to run all of their cardiac markers as STATs, rather than risk a delay. The downside of this policy, however, is that STATs disrupt the workflow and backlog routine work.”

To speed the sample preparation process, StatSpin developed the StatSpin Express 2 to be used as a dedicated STAT centrifuge to improve overall process efficiency. As such, it complements - rather than competes against - conventional, high-volume laboratory batch centrifuges. Reportedly, more than 10,000 StatSpin units are now in the clinical and veterinary fields, typically situated in proximity to analyzers from all leading manufacturers, including those made by Beckman Coulter, bioMerieux, DPC, Abbott, Ortho, Tosoh, Roche, Bayer and IDEXX.

Mello explains, “If an ER switches from a serum-based sample to plasma and positions a dedicated StatSpin Express 2 unit near a POC analyzer, centrifugation of the sample can be accomplished in three minutes or less. So it’s possible to reduce the turnaround time by 30 to 35 minutes compared to performing centrifugation in a central lab. Tubes go directly to the analyzer station where they can be processed serially as they arrive. There’s no need to wait for batch processing, and there’s no need to disrupt the workflow in the pre-analytical sample processing area of the central lab. Moreover, it’s easier to safeguard the sample because the reduced handling and transportation minimizes the chance of breakage or mix-ups with other specimen tubes.”

Widespread acceptance of the concept
The effectiveness of the StatSpin Express 2 has been demonstrated in a number of published technical papers. For example, Mello cites one by Kimberly Foster, et al., of Bayer Corporation, Diagnostic Division (“Evaluation of a Centrifuge with Rapid Turnaround Time for the Preparation of Plasma Samples for Measurement of Common STAT Markers on the ACS: 180 System”, Clin. Lab. 2000; 46: 157-160). This paper concludes, “In our studies the accuracy of results of six different assays with the StatSpin method has been shown to be the same as the conventional separation method. For these reasons, the StatSpin method may be considered as a positive addition to any laboratory that is concerned about rapid turnaround time of blood processing. This method can be of great utility not only for samples where STAT answers are required, but also for samples where the analyte may be especially labile and where sample handling is critical.”

Another concern sometimes voiced about performing rapid centrifugation relates to how well samples produced by fast centrifugation correspond to those produced on slower speed laboratory centrifuges. Mello says that a good correlation comes from bioM´erieux, a supplier of the D-dimer assay, a rapid diagnostic test used in ER triage units to screen patients for pulmonary embolism and venous thrombosis. bioM´erieux conducted a study to compare the quality of samples recovered by rapid centrifugation on the StatSpin versus that of samples recovered by conventional centrifugation. The results reported for the two methods were virtually identical, with a 0.996 “R” factor or coefficient of correlation between samples.

Comparable advantages in settings outside the ED Clinics
Rapid diagnostic tests are used with increasing frequency in a variety of clinical settings. Says Mello, “Fast centrifugation of samples means that clinicians can provide their patients with results while they are still on the premises.

The added efficiency helps reduce patent anxiety, and also minimizes the need for follow-up telephone calls to schedule subsequent patient visits.”

Operating Rooms
Another application area for the StatSpin Express 2 is the OR. Mello cites a new test for intra-operative biointact PTH (parathyroid hormone). He says, “This assay is intended for the instant monitoring of intact PTH levels during parathyroid surgery. It requires serum and plasma, and involves a two-minute incubation time and a nine-minute test time to first results. So again we’re talking about the need for rapid answers. The patient is on the table while everyone is waiting for the answer to determine the efficacy of the surgical procedure.”

Central Labs
Even in central labs, away from point of care environments, the StatSpin Express 2 offers rapid turnaround advantages when used with chemistry, coagulation, immunoassay, and other types of analyzers. In the laboratory environment, just as in the ED, users typically dedicate a StatSpin Express 2 to each analyzer. Given its compact size, it fits on almost any available bench space.

Says Mello, “These centrifuges are widely used in the coagulation market. A coagulation test requires a platelet-poor plasma, and our product can provide the required specimen in two minutes. This has important ramifications for the OR, too because a lot of coagulation testing is done pre-operatively or during surgery while the patient is bleeding.”

Technical features and performance
Designed to spin four sample tubes at a constant speed of 8500 rpm, the StatSpin Express 2 incorporates a patented drive and suspension system that provides fast acceleration and deceleration, quiet vibration-free operation, jostle-free braking, and fast “eyeball” balancing of loads with up to 1/2 gram of imbalance.

Mello says, “The combination of higher centrifugal force along with the high efficiency rotor design permits faster sample separation than possible with a conventional batch centrifuge. Barrier distortion is minimized, allowing use of the tubes on most automatic sampling equipment without concern for contaminating the sample probe. Moreover, there is no sacrifice in sample integrity. Studies of the StatSpin’s ability to recover cardiac markers in the ER environments have shown an “R” correlation factor of 0.99 compared to conventional centrifuges located in central labs.”

Running under microprocessor control, the unit is equipped with on-board diagnostics and error code lights to facilitate operation and aid in troubleshooting (i.e., open lid, out-of-balance rotor, etc.). To operate, the user selects one of three preprogrammed spin settings: 30 seconds, 2 minutes, and 3 minutes. This “load and go” approach avoids the problem of different users randomly changing speed and time settings.

A set of inserts (four different sizes) is provided to accommodate glass or plastic tube formats, including gel tubes, from 1.5 ml to 5 ml. No maintenance is required other than periodically cleaning the liner and rotor with a 10 percent bleach solution. For safety, the UL approved and CE marked centrifuge has both a mechanical and an electrical latching system to secure the clear Lexan lid. The rotor must be at rest before the lid can be opened. A built-in fan prevents overheating by limiting sample temperature rise to less than 7ÞC, even under heavy use. Usable worldwide without modification, the unit is powered by 100 to 240 volts AC, 50-60 Hz. A 1-year warranty is provided, backed up by toll-free telephone support.

Associated consumables
StatSpin also offers a number of consumable products for use with the StatSpin Express 2, including replacement inserts for tubes, disposable chamber liners, replacement rotors, and LipoClear, a reagent used for clarifying lipemic specimens during centrifugation. With this reagent, clarification takes 3 minutes in the StatSpin Express 2 and 20 minutes in a conventional centrifuge.

Available from leading health care distributors worldwide, the StatSpin Express 2 sells for about 20 - 25 percent of the cost of a large batch-processing centrifuge with a 24 - 48 tube capacity.

Gary Wolfe is a freelance writer based in Franklin, Mass.