Over Dr Dubin’s long (he has been in practice for over sixty years) and successful career as a US-based vet he has seen an increasing reliance on ‘tests’ as opposed to physical/clinical examinations when making a diagnosis. Labour-intensive ‘bench’ type tests have been replaced by machines which are analysed, often remotely, by computer programmes and more recently with the use of artificial intelligence (AI). Moreover, batteries or panels of tests are done pre-emptively or for screening rather than to confirm the findings of physical diagnosis. In deciding whether a screening procedure is desirable, consideration must be given to the prevalence of the problem in the target population, lest a preponderance of false-positive results distort the picture. When large panels are done – as compared to single or few targeted tests, the ‘curse of dimensionality’ may lead to falsely attributing importance to any single test. Notwithstanding the potential benefit of tests, their growing role in veterinary diagnosis has increased cost and dependence on external (possibly scarce) resources.
Introduction
Over my 60 plus years as a veterinarian, I have seen my profession morph towards mechanisation, commercialisation, and increased costs; and away from the artisanal labour-intensive ‘noble calling’ to which I aspired as a youth. These changes may offer more predictability; and, ostensibly, improved outcomes. However, they come with substantial cost and erosion of the veterinary clinical relationship. Nothing highlights this more than the evolution of ‘tests’. I use the word ‘tests’ to cover clinical data other than physical diagnosis i.e. laboratory studies of blood and urine, as well as imaging (x ray, ultrasound, CAT scan), and EKG. I would divide the totality of diagnostic information into the physical diagnosis (listening, feeling, smelling, looking) and the above-named tests.
I don’t want to underrate the value of tests in veterinary medicine. Indeed, I have devoted much of my professional life to the development of such procedures. My concern is that the role of tests has shifted away from being necessary confirmatory procedures, conducted based on a working physical diagnosis. They have tended, rather, to become pre-emptive crutches for indolent doctors, and to conform to a more hierarchical corporate model of veterinary medicine. Some tests have also seem to have become cash cows, driven primarily by financial gain rather than diagnostic necessity.
During the first week of veterinary college, we were told of our required equipment. This included stethoscope, otoscope ophthalmoscope set, plexor/pleximeter, dissection tools, lab coats, overalls, obstetrical sleeve, and; most notably, a microscope. The microscope was the most expensive item in our school budget; but we were assured that we should expect to use it personally every day of our professional careers. We were also required to own a hemacytometer set. All of this kit points to the artisanal labour-intensive perspective with which we faced our professional lives. I wonder how many vets nowadays regularly use a microscope.
An important lesson
After graduation I was employed by a vet called Dr Carlton Hower, who sat in on my initial consultations. My first case involved a dog with a persistent, hacking cough that kept his owners awake at night. The dog also showed hesitancy towards eating and had recently been boarded at a kennel. Upon physical examination, I noticed a mild fever (103.6°F), reddening of the throat, and enlargement of some lymph nodes in the neck. Otherwise, the dog appeared lively, alert, and playful. Dr Hower took me aside and asked my opinion. I advised a chest X-ray, a throat culture, and a CBC (complete blood count). I proposed that the clients should call back in three days to receive the results and discuss the appropriate treatment. He burst into laughter. ‘Do you believe we should charge these kind people $38.00 and send them home without providing any relief for their suffering dog, not to mention their peace and quiet?’ ($38? It was 1964!). Dr Hower then pointed out the clear indications of kennel cough’ aka tracheobronchitis. He remarked that a creditable veterinarian could initiate treatment based on the symptoms, history, and physical examination alone, without the need for laboratory tests or delays. Following his advice, I injected long-acting penicillin combined with a steroid and dispensed tablets which contained codeine and an antihistamine. I counselled the owners that if their pet did not improve or encountered any further issues, we could then conduct additional tests. The dog made a quick and full recovery. I had learnt the difference between the academic viewpoint and practical horse sense.
To test or not to test
My second practice employer was Dr. Marty Pearl, of blessed memory. He had a small-animal practice in urban Philadelphia. As with many veterinary establishments of the time, the practice was in his own home. The practice office (waiting room, examining room, surgery, and grooming area) were on the first floor while the Pearl family lived on the upper two floors. The basement and backyard were dedicated to boarding and ‘recovery’ wards. Like many other veterinarians, Dr. Pearl had a do-it-yourself ‘sustainable’ laboratory.
This meant that we conducted most laboratory testing on-site using simple, reusable supplies and equipment; while current practices often send samples to external laboratories or use expensive single-use point-of-care kits.
Heartworm disease is a grave ailment affecting dogs and, potentially, cats, wherein worms reside in the heart and blood vessels Predictably, this interferes with blood flow and compromises the proper functioning of the heart valves. Heartworm is transmitted by mosquitoes and was relatively rare in our area (Pennsylvania) at the time as it probably is now. Dr. Pearl employed a remarkably straightforward testing method. A drop of the patient’s blood was placed on a glass slide and examined under a microscope. The presence of moving larvae (microfilariae) indicated infection. Although not foolproof, this method was very selective, i.e. when the larvae were seen, the diagnosis was certain. Furthermore, it was immediate and cheap, costing only a few pennies. In comparison, the more modern and now common immunologic tests are expensive and although highly sensitive, they also pose the risk of false positives, particularly in areas where heartworm disease is infrequent. (Although heartworm is not endemic in the UK, the number of heartworm infections diagnosed in dogs in the UK is increasing, with most cases found in dogs that have travelled to or been imported from areas where the disease is endemic, such as southern and eastern Europe). In my opinion tests should be used primarily to confirm a working diagnosis.
To conclude
When I began my veterinary adventure tests were a hybrid of science and handicraft. The procedures were skilful, painstaking; and often tedious. The process was labour-intensive, but immediate and moderate in cost. Blood and urine chemistry often required mixing reagents, heating and observing a colour change. Imaging, such as taking X-rays, involved developing films in the dark listening to flowing water. Blood counts involved long periods peering through a microscope with a clicker to enumerate the cells. Most often, now, such tasks are relegated to machines – either at central laboratories or in the practice facility. The machines are rapid, precise, convenient and expensive to purchase, maintain and supply. Often, they are connected to the cloud. As a result, using digital radiography or ultrasound, a veterinarian can press a button; and within, minutes receive a consultation (at additional cost) from a specialist (or a robot) across the globe. Much of the tedium and eyestrain has gone out of tests. Regardless of the cost to the practice, they are considerably more expensive for the client. Fear is sometimes used to sell test (under the guise of ‘better safe than sorry’) and so is the idea of performing a panel of tests to see if they reveal anything (under the guise of ‘preventative medicine’). In 1964, Abraham Kaplan gave voice to the often repeated Law of the Instrument: ‘Give a small boy a hammer and he will find that everything he encounters needs pounding.’ To which I would add: ‘Especially if the hammer is expensive.’ In sixty years of veterinary practice, I have seen a remarkable increase in the contribution of ‘tests’ to veterinary diagnosis. In some part, this is due to improvement in the tools available to doctors. Regrettably, it may also reflect relative de-emphasis on skilled personal observation and listening skills. It often results in increased cost in the face of limited resources that must be shared with good nutrition, housing, play and other factors contributing to quality of life for our pets. I hope my grouchy ruminations stimulate you to seek a balanced holistic view of testing.
By Dr. Stephen Dubin V.M.D.
