Are current methods of measurement of erythropoietin (EPO) in human plasma or serum adequate for the diagnosis of polycythaemia vera and the assessment of EPO deficiency?

Acute normobaric hyperoxia transiently attenuates plasma erythropoietin concentration in healthy males: evidence against the 'normobaric oxygen paradox' theory

AIM

The purpose of the present study was to evaluate the 'normobaric oxygen paradox' theory by investigating the effect of a 2-h normobaric O(2) exposure on the concentration of plasma erythropoietin (EPO).

METHODS

Ten healthy males were studied twice in a single-blinded counterbalanced crossover study protocol. On one occasion they breathed air (NOR) and on the other 100% normobaric O(2) (HYPER). Blood samples were collected Pre, Mid and Post exposure; and thereafter, 3, 5, 8, 24, 32, 48, 72 and 96 h, and 1 and 2 weeks after the exposure to determine EPO concentration.

RESULTS

The concentration of plasma erythropoietin increased markedly 8 and 32 h after the NOR exposure (approx. 58% and approx. 52%, respectively, P ≤ 0.05) as a consequence of its natural diurnal variation. Conversely, the O(2) breathing was followed by approx. 36% decrement of EPO 3 h after the exposure (P ≤ 0.05). Moreover, EPO concentration was significantly lower in HYPER than in the NOR condition 3, 5 and 8 h after the breathing intervention (P ≤ 0.05).

CONCLUSION

In contrast to the 'normobaric oxygen paradox' theory, the present results indicate that a short period of normobaric O(2) breathing does not increase the EPO concentration in aerobically fit healthy males. Increased O(2) tension suppresses the EPO concentration 3 and 5 h after the exposure; thereafter EPO seems to change in a manner consistent with natural diurnal variation.

Procedures for monitoring recombinant erythropoietin and analogues in doping control

The present report summarizes the main analytical strategies developed to identify the presence of recombinant erythropoietin (EPO) administered as a doping agent. Indirect evidence is based on the analysis of blood parameters (haemoglobin, haematocrit, reticulocytes, macrocytes, etc.) and serum markers (concentration of EPO and serum transferrin receptors, etc.). The problem of intertechnique comparison for reliable results evaluation is emphasized, especially for serum markers. Charge differences between isoforms of recombinant EPO and native urinary EPO are the grounds for the isoelectric focusing-double blotting-chemiluminescence detection method presently approved for doping control. Works addressing its advantages and limitations are presented and commented on. The chemical bases of the differential detection are highlighted and some future approaches for detection are also presented. The appearance and detectability of EPO analogues and mimetics susceptible for abuse are also addressed.

Hydroxyurea therapy increases plasma erythropoietin in patients with essential thrombocythaemia or polycythaemia vera

The determination of serum/plasma erythropoietin (EPO) concentration has gained widespread use in the diagnosis of polycythaemia vera (PV). A reduced EPO concentration in a newly diagnosed essential thrombocythaemia (ET) seems to be a risk factor for thromboembolic events. In this study plasma EPO concentration was determined before and after initiated hydroxyurea (HU) therapy, 14 patients with PV or ET were included. After 1 month on HU therapy 11 of 14 patients had increased their EPO concentration compared with prior to medication. The plasma EPO was increased in all, except one patient, after 4 months HU therapy. If EPO is incorporated in the diagnostic or prognostic procedures it should be determined before myelosuppressive therapy is initiated.

Management of patients with polycythaemia vera: results of a survey among Swedish haematologists

The prevailing attitudes regarding diagnostic and therapeutic procedures in patients with polycythaemia vera (PV) among Swedish haematologists were surveyed by way of a mailed questionnaire in August 2002. Among diagnostic procedures frequent use is reported for arterial O(2) saturation, spleen size determination, bone marrow histology, serum erythropoietin, serum cobalamins and leukocyte alkaline phosphatase score, while direct determination of the red blood cell mass is used infrequently (seldom or never by 82%). Among therapeutic modalities hydroxyurea and phlebotomy alone were most frequently used. The (32)P therapy was used at least sometimes by 57% of the physicians, and more widely in the university clinics. Anagrelide and alfa-interferon was used in a minority of patients only. The use of prophylactic acetylsalicylic acid was very variable. The majority of the physicians had an aim for their phlebotomy treatment at a level of 0.45 or less, but 21% used a level of 0.46-0.49 and 8% a level of 0.55-0.60 (in younger patients). The platelet level, at which myelosuppressive therapy was initiated, also varied, from 400 x 10(9)/L to >1500 x 10(9)/L. It can be concluded that in practical clinical work in Sweden the diagnosis of PV is established by frequent use of serum erythropoietin, bone marrow examination and spleen size determination. The use of different therapeutic modalities is very variable. Many physicians carry out their phlebotomy treatment with less intensity compared with national and international recommendations.

Evaluation of immunoassays for the measurement of erythropoietin (EPO) as an indirect biomarker of recombinant human EPO misuse in sport

The measurement of serum erythropoietin (EPO) has been proposed as one of the indirect biomarkers for the detection of recombinant human EPO misuse in sport. An extended inter-laboratory validation of two commercial immunoassays for EPO measurement is described. A chemiluminescent immunoassay kit (CHEM) and an enzyme-linked immunosorbent assay kit (ELISA) were evaluated. The CHEM assay showed intra-laboratory precision better than 6% and correct accuracy values for all quality control samples tested. Precisions and accuracies better than 7 and 13%, respectively, were obtained for the ELISA assay for most of the quality control samples. The limit of quantification estimated for CHEM assay was lower than for the ELISA assay. Inter-laboratory concordance was good for both the assays, with lower dispersion shown by the CHEM assay. Results obtained with the ELISA assay were always lower than those of the CHEM assay. However, a good inter-technique correlation was obtained ([ELISA]=0.76 [CHEM]+0.06, r2=0.92). Quality control samples had a good stability after one and two freeze/thaw cycles and in simulated transportation conditions. In conclusion, CHEM and ELISA assays showed similar characteristics regarding intra-laboratory validation. Better inter-laboratory results were obtained with the CHEM assay and, hence, it is considered the recommended assay for anti-doping control analysis.

The presence of a significant association between elevated PRV-1 mRNA expression and low plasma erythropoietin concentration in essential thrombocythaemia

Approximately 45% of newly diagnosed patients with essential thrombocythaemia (ET) demonstrate subnormal plasma erythropoietin (EPO) concentrations, which constitutes a risk factor for occlusive vascular events. In 58 ET patients, a possible association between polycythaemia rubra vera-1 (PRV-1) overexpression and subnormal plasma EPO was investigated, which was always measured prior to the institution of platelet lowering agents. At the time when PRV-1 expression was measured, 28 of 58 (48%) ET patients had received platelet lowering treatment. PRV-1 expression was measured by quantitative real-time reverse transcription-polymerase chain reaction assay of mRNA extracted from purified peripheral blood buffy coat. The cycle threshold (CT) value of PRV-1 was determined and was divided with the CT value for the housekeeping GAPDH gene transcript. A quotient <0.93 was defined as PRV-1 positive. Of the ET patients 12 of 58 (21%) were PRV-1 positive and 19 of 58 (33%) demonstrated subnormal plasma EPO. In the 58 ET patients there was a significant association between low plasma EPO and PRV-1 positive results (P = 0.001). The 30 ET patients who had not received any platelet lowering treatment showed a significant (P = 0.005) relation between PRV-1 positivity and subnormal plasma EPO. No such relationship was present in the 28 ET patients who had received prior treatment with the above drugs (P = 0.147).

Serum erythropoietin values in erythrocytoses and in primary thrombocythaemia

Serum erythropoietin (Epo) values were estimated in samples from 125 patients with erythrocytosis to examine the specificity and sensitivity of reduced and raised values in the diagnosis of polycythaemia vera (PV) and secondary erythrocytosis (SE) respectively. Additionally, Epo values were estimated in samples from 49 patients with primary thrombocythaemia (PT) to determine whether Epo values were altered. We found high specificity (92%) and moderate sensitivity (64%) of low serum Epo values (below the reference range) in the diagnosis of PV, and also poor sensitivity (47%) of raised Epo values in the diagnosis of SE. Raised Epo values were not observed in PV patients with Hb > 14.0 g/dl and were only observed in one PV patient with a relatively low Hb recovering from a gastro-intestinal haemorrhage. Raised Epo values occurred in some patients with apparent erythrocytosis (AE) and idiopathic erythrocytosis (IE), mainly at normal (rather than raised) Hb values (< 16 g/dl). Low Epo values occurred in a few AE, IE and SE patients at higher Hb values (> 16 g/dl). Low Epo values were less specific for PV when the Hb was raised, while raised Epo values were less specific for SE when the Hb was not raised. Approximately one third of patients with PT had a low (below the reference range) Epo value, this being associated with a high normal Hb (> 14 g/dl, P < 0.001) and showing a trend towards association with absence of treatment. The high normal Hb values were in turn associated with an increased incidence of thrombotic events (P < 0.05). These findings could influence the future investigation and management of PT patients.

On the diagnosis of polycythaemia vera as assessed in the health and medical care in the Västra Götaland region, Sweden

OBJECTIVES

The aim was to assess how the diagnosis of polycythaemia vera (PV) was established and to study to which extent the classic Polycythemia Vera Study Group (PVSG) criteria and the revised criteria for the diagnosis of PV as proposed by Pearson and Messinezy in 1996 (PM criteria) were fulfilled when the diagnosis of PV was made.

DESIGN AND SETTING

A questionnaire was sent to physicians in charge of haematological patients at the departments of medicine in 12 hospitals in the Health and Medical Care in the Västra Götaland Region (VGR), Sweden, with a population of 1.5 million inhabitants; they were asked to provide reports as regards all patients with an unequivocal diagnosis of PV during a 5-year period from January 1994 to December 1998.

SUBJECTS

Full reports were obtained from six hospitals, which serve about 1.1 million inhabitants. The results from a total of 129 PV patients, 62 from two university hospitals (UHs) and 67 from four county hospitals (CHs), were the subject of the present analysis. Results. It was shown that measurement of the red cell mass (RCM) had been carried out in 61 of 62 (98%) patients in UHs compared with 24 of 67 (36%) patients at CHs (P < 0.01). By using ultrasound imaging and/or scintigraphy the spleen size had been determined in 55 of 62 (89%) patients at UHs and in 24 of 67 (36%) patients at CHs (P < 0.01). At the UHs, arterial oxygen saturation had been measured in 32 of 62 (52%) patients; the corresponding figure for the CH patients was 22 of 67 (33%). Plasma or serum erythropoietin (EPO) concentrations had been measured in 44 of 62 (71%) of PV patients at UHs and in 31 of 67 (46%) of patients at CHs; in all these cases the EPO concentrations were subnormal or not measurable.

CONCLUSIONS

At the UHs only 37% of the PV patients fulfilled the PVSG criteria for the diagnosis of PV whereas the corresponding figure for CHs was 4% (P < 0.01). The adherence to PM criteria was, however, 71% at UHs compared with 16% at CHs (P < 0.01).

New automated chemiluminescent assay for erythropoietin

Erythropoietin (EPO) is a polypeptide hormone produced by the kidney that regulates erythropoiesis by controlling the proliferation and differentiation of erythroid progenitors in bone marrow. Assays for EPO are used to monitor dosage and response to human recombinant erythropoietin also may have diagnostic utility in the differential diagnosis of anemia and polycythemia. We evaluated an automated, chemiluminescent immunoassay for EPO (DPC Immulite) in terms of precision, linearity, interference, and correlation with reference assays. The Immulite assay demonstrated acceptable correlation with the reference immunochemiluminometric method (slope = 1.087, y intercept = 0.567, R value = 0.990). Within-run CVs ranged from 2.3% to 5.0%, while between-run CVs ranged from 4.1% to 9.5%. Linearity extended beyond the manufacturer's stated claims, and recovery ranged from 96.8% to 100.9% across the concentrations tested. No significant interference was noted with hemoglobin, bilirubin, or triglyceride. Overall, this method compares favorably with the existing immunochemiluminometric reference method and offers clinical laboratories an alternative for the analysis of erythropoietin.

Serum erythropoietin in heart failure patients treated with ACE-inhibitors or AT(1) antagonists

BACKGROUND

Erythropoietin (Epo), a growth factor produced by the kidney, is important in heart failure patients to promote oxygen delivery to tissues. Seventy-two chronic heart failure (CHF) patients at our outpatient clinic were subjected to morning serum Epo-level measurements and classified according to NYHA criteria.

RESULTS

Forty-eight patients of classes III and IV had a significantly elevated serum Epo-level of 42.9+/-40.3 mIU/ml (mean+/-1 S.D.) when compared to the mean level of 24 patients of classes I and II who had a normal range mean value of 13.4+/-6.2 mIU/ml (P<0.05). Patients on angiotensin-converting enzyme (ACE) inhibitors showed a trend towards lower serum Epo-levels compared to patients treated with angiotensin-II type-1 receptor antagonists (AT(1) antagonists) (levels: 33.3+/-35.6 mIU/ml and 43.6+/-38.1 mIU/ml). This trend did not, however, reach statistical significance (P=0.36).

CONCLUSION

We suggest that a desirable Epo increase in class III and IV CHF patients could be achieved by either recombinant human Epo administration or, possibly, by appropriate selection of the concomitant medical therapy. A large prospective study shall investigate the possible advantage of AT(1) antagonists over ACE-inhibitors with regard to Epo effect.

Laboratory screening for erythropoietin abuse in sport: an emerging challenge

The growing diffusion of banned practice to improve the athletic performances is forcing clinical laboratories to identify and standardize reliable assays to detect potential unfairness. Among the doping practices, the use of recombinant human erythropoietin is becoming fairly popular, due to simplicity and safeties of administration and troublesome detection. The heterogeneous response rate, the presence of a little but significant amount of naturally occurring hormone, the short half-life exhibited by recombinant human erythropoietin and the lack of standardization of commercial assays appear the main problems to overcome. Aim of the present article is to provide a critical review of some of the more widespread laboratory techniques currently available for the screening for erythropoietin abuse in sport.