Are we drawing too much blood?

Are we drawing too much blood?

Agreat number of laboratory instruments perform highly reliable analyses, down to the picogram level, on 8 to 200 l of specimen --and often on less. These smaller sample sizes evolved over the last 15 years through competition among manufacturers to produce more efficient analyzers.

Unfortunately, blood drawing practices haven't changed with the technological capabilities in many labs. Much more blood is taken than is needed.

The problem ranges beyond the requirements of individual instruments. Different lab sections often work on separate specimens from a single patient. Why can't they share the same specimen?

Specimen sharing would call for a whole new set of laboratory procedures. If such a system is established and instrument capabilities are taken into account, phlebotomy techniques also have to change, in line with the reduced demand for patient blood.

Before considering what steps must be taken, let's look at the issue from a first-time patient's point of view. Imagine a young executive who complains of chest pain and finds himself in a hospital for the very first time. He is terrified of the emergency room and convinced he has had a heart-attack. I firmly believe that if he hasn't yet had a coronary, the sight of a technician armed with five or six tubes for phlebotomy may bring one on. We forget how frightening our routine procedures can seem. The array of tubes, the volume drawn, and the frequency of venipunctures confuse patients. They start worrying about the severity of their illness.

It is not our job to challenge physicians about the nature and frequency of test requests, although I sometimes wish we could. But we can relieve patient anxiety and discomfort by exercising good management of blood specimens.

The amount of blood drawn should be sufficient to perform each test under the specific analytical procedures to be used, and also enough to repeat tests in case of technical difficulty, instrument failure, accidents, abnormal results, or requests for confirmation. On occasion, it may be necessary to run a test four times. So if an instrument requires 50 l of blood, 1 ml is a safe level to draw, and it's still much less than the 10 to 15 ml routinely taken per test.

Taking 300 l as an average sample requirement, seven tests on different instruments would necessitate a little more than 3 ml of blood. That's far from a full tube. Different work stations and sections could usually share this amount of blood or a larger quantity within a single tube.

How? By setting up a laboratory specimen bank and distribution center. The center would receive all test requisitions and be responsible for all blood drawings. With computer assistance if possible, it would keep track of specimens in the laboratory--not only noting the quantity and location, but also information about fasting conditions, types and time of patient medication, and other pertinent data. No specimen would be drawn before a thorough inventory search in the laboratory to locate a possibly suitable specimen. Runners would transport specimens from section to section.

This can go a long way toward eliminating repeat drawings. The benefit is especially apparent in cases where the patient is visited by more than one physician. In ordering additional tests, the second clinician on the scene may not realize that blood has already been drawn.

Admittedly, there are numerous conditions that dictate a series of specimens, such as glucose tolerance testing or therapeutic drug monitoring assays before and after medication. But these various specimens can be used elsewhere as well.

A specimen for digoxin testing, for example, is drawn four to six hours after a dose has been administered. What's left over from that specimen can be used for later test requests: a VDRL latex, C-reactive protein, bilirubin, cholesterol, or thyroid study. Even yesterday's serum is suitable for VDRL and many other tests when properly identified. Drawing the patient again should be a last resort.

Phlebotomy and test procedures will change if conserving patient blood becomes a more important goal. As we have noted, less than full evacuated tubes can be drawn. However, some observers say this causes pain to the patient. If collection requirements are changed, perhaps manufacturers will finally provide smaller tubes. In addition, fingerstick specimens may be used when full tubes are not needed for hematology studies.

If microanalysis works in pediatrics, there's no reason why it should not work for adults, too. The idea is at least to try using smaller amounts to minimize patient discomfort.

Smaller specimens lead to lower supply and reagent consumption. Blood kept within the patient does not need refrigeration or freezing. It never becomes a leftover that has to be autoclaved or incinerated.

More important, prudent specimen management conserves the most precious asset a patient has. It is particularly vital to geriatric, pediatric, burn, and oncology patients who have extremely limited blood resources.

Here is an instance where cost containment and patient interests are in perfect harmony.