This Sporting Life

Clinical pathology data play an important role in advancing sports  medicine. Biochemical and hematological parameters help assess the health of recreational and professional athletes, prevent infectious diseases and injuries, measure performance, and, detect the use of illicit and unethical substances or methods (1) (something that is becoming ever more important given the recent negative media attention that doping in athletes has gained). As a result, the preanalytical phase is crucial for evaluating and interpreting clinical data, especially when laboratory results may have legal consequences for the athlete.

Specific knowledge in this area has burgeoned in recent years resulting in much more awareness about the correct drawing, transport and storage of biological material. In fact, both The European College of Sport Science and the American College of Sports Medicine have warned of the influence of preanalytical factors – time of blood drawing, food intake, time of analysis after the end of exercise, gender, age, etc. – on laboratory data (2).

Given the rising number of controversies in athletic sports regarding illicit drug use, anti-doping programs strongly promote and support the measurement of biochemical and hematological parameters in athletes; but, there are some challenges to following the guidelines. For example, fasting is crucial for most laboratory parameters, but in sports medicine it is not easy – and sometimes impossible – to define, perform, organize, and (or) control it.

During a three-week-stage cycle race, for instance, athletes will follow a 6,000 kcal a day diet, consuming 1,500 kcal each morning before the start of each stage. Because food intake may influence many laboratory parameters, this makes correct blood drawing difficult. Also, clinically significant variations in neutrophils, eosinophils, erythrocytes, hematocrit volume (packed cell volume) and mean corpuscular hemoglobin levels occur up to four hours after eating. There are also increases in alkaline phosphate (ALP), triglycerides, albumin, calcium, sodium, magnesium, potassium, C-reactive protein (CRP), uric acid, bilirubin, alanine transaminase (ALT) and aspartate aminotransferase (AST). And, in endurance sports, athletes must eat continuously to restore glycogen. You see the challenge…

So, when evaluating biochemical and hematological parameters, blood dilution or concentration needs accurate definition. The Dill & Costill equation, which is based on the concentration of hemoglobin and on the percentage of hematocrit before and after exercise, is accepted in scientific literature for correcting the alteration in erythrocyte concentration in plasma due to physical activity. The equation requires the immediate analysis of hematological specimens and it’s been recently proposed that it can be used for calcium too, which is helpful for monitoring a range of conditions relating to bones, heart, nerves and kidneys (3). Recent research has also demonstrated that, with a modification, it could also be used at different environmental temperatures (4).

Such is the emphasis that is placed on blood monitoring of athletes, the “Athlete Biological Passport” has been designed to store data on athletes’ hemoglobin concentration and the percentage of reticulocytes over time. While the preanalytical factors that can influence hemoglobin are known, those that affect reticulocytes, especially during physical exercise, required in-depth study and evaluation before they could be included in the athletes’ biological passports (5,6).

Reticulocytes have higher intraindividual variability in athletes than in nonathletes. They also have high interindividual variability, even in homogeneous athlete populations. Only by monitoring reticulocyte values in a single subject over time can this variability be accounted for and an accurate interpretation made.

Interestingly, it’s difficult to compare scientific studies on reticulocytes. They are less stable than hemoglobin, and their stability depends on the method used for counting; storage at cold temperatures (ideally 4°C) is required to guarantee stable values. Acute exercise does not modify reticulocytes, but training and competitions during a season does influence their values. Also, the differences between consecutive seasons are greater than those within a season in the same group of athletes. It is especially remarkable that reticulocyte modifications noted during the season do not always follow those seen in hemoglobin.

In my view, the preanalytical phase is fundamental for assuring correct interpretation of laboratory data. To assure accuracy, all preanalytical variables should be documented and referenced when evaluating laboratory results in sports medicine. After all, an inaccurate laboratory result has the potential to change an athlete’s life – for better or for worse.