Definition and application of performance specifications for measurement uncertainty of 23 common laboratory tests: linking theory to daily practice

Laboratories should estimate and validate [using analytical performance specifications (APS)] the measurement uncertainty (MU) of performed tests. It is therefore essential to appropriately define APS for MU, but also to provide a perspective on suitability of the practical application of these APS. In this study, 23 commonly ordered measurands were allocated to the models defined during the 2014 EFLM Strategic Conference to derive APS for MU. Then, we checked if the performance of commercial measuring systems used in our laboratory may achieve them. Most measurands (serum alkaline phosphatase, aspartate aminotransferase, creatine kinase, γ-glutamyltransferase, lactate dehydrogenase, pancreatic amylase, total proteins, immunoglobulin G, A, M, magnesium, urate, and prostate-specific antigen, plasma homocysteine, and blood red and white cells) were allocated to the biological variation (BV) model and desirable APS were defined accordingly (2.65%, 4.75%, 7.25%, 4.45%, 2.60%, 3.15%, 1.30%, 2.20%, 2.50%, 2.95%, 1.44%, 4.16%, 3.40%, 3.52%, 1.55%, and 5.65%, respectively). Desirable APS for serum total cholesterol (3.00%) and urine albumin (9.00%) were derived using outcome-based model. Lacking outcome-based information, serum albumin, high-density lipoprotein cholesterol, triglycerides, and blood platelets were temporarily reallocated to BV model, the corresponding desirable APS being 1.25%, 2.84%, 9.90%, and 4.85%, respectively. A mix between the two previous models was employed for serum digoxin, with a 6.00% desirable APS. In daily practice by using our laboratory systems, 16 tests fulfilled desirable and five minimum APS, while two (serum albumin and plasma homocysteine) exceeded goals, needing improvements.

P394 FROM A PET THE FIRST AND UNEXPECTED DIAGNOSTIC ORIENTATION

Introduction

Nuclear medicine plays an important role in the diagnosis and treatment of numerous pathologies. In the cardiology field it can be used to obtain a lot of information about ischemic heart disease, infiltrative heart disease and inflammatory and infectious diseases such as endocarditis. The greatest impact in the field of these latter pathologies was obtained using F–fluorodeoxyglucose (FDG) in the study of patients with implantable electronic devices and replaced valves or valve prostheses. In this regard, I report the case of a patient with results of valve tube implantation in which a PET performed to investigate an inflammatory pathology has allowed to make a diagnosis of endocarditis.

Discussion

The case concerns a 66–year–old man subjected to intervention of Bentall for type A aortic dissection (in 2015); chronic aortic dissection remains (Stanford B). Diabetic with chronic renal failure and COPD. Recovered in medicine for low back pain, dysuria and episodes of chills without pyrexia. High inflammatory indices but with urine culture and negative blood cultures performed on isolated febrile peak. CT scan of the chest negative for phlogistic localizations and for intense rachialgia in the suspicion of spondylodiscitis is subjected to total body PET that shows accumulation of radio compound in the first tract of the ascending aorta with greater anterior focality: hyper fixation is associated at the level of the lower limiter of L4 and L5. With these results therefore posed the suspicion of endocarditis for which started to perform transthoracic echocardiogram that did not identify certain pathological elements and transesophageal elements that instead showed suggestive images for endocarditic vegetation in aortic mechanical prosthesis (intravalvular mobile filiform appearance) and on the atrial side of the tricuspid valve (“soft” appearance of large dimensions). It is not associated with valvular dysfunction. After the echocardiographic finding, therapy with daptomycin in addition to piperacillin/tazobactam is initiated and the patient transferred to the infectious diseases department.

Conclusions

Bacterial endocarditis in particular in patients undergoing cardiac surgery or wearing implantable devices is often characterized by unusual clinical presentation as in this case, so it is not excessive to resort to second–level imaging such as transesophageal echocardiography and nuclear cardiology diagnostics.

P55 A CHALLENGING RIGHT ATRIAL MASS

A 64–year–old woman presented at the Emergency Department with worsening dyspnoea and fever. Blood tests revealed normal white blood count, elevated C–reactive protein (244 mg/L) and D–dimer (2618 ng/mL). At arterial blood gases test hypoxaemia and hypocapnia was found (pH 7.48, pO2 83 mmHg, pCO2 30 mmHg, base excess –1.2 mmol/L, lactates 1.0 mmol/L). She underwent thoracic computed tomography (CT), which showed right inferior pulmonary embolism with infarction. A transthoracic echocardiography (TTE) revealed the presence of a mobile heterogeneous iso–hyperechoic neoformation completely occupying the right atrial cavity and moving partially across the tricuspid valve (Figure 1). A right atrial thrombotic formation was hypothesized and, due to its dimension, despite a valid hemodynamic, the patient underwent thrombolysis with rtPA 100 mg iv infusion over 2 hours. However, the next day at CT and TTE the mass was still there and unmodified. The screening for thrombophilia and for cancer markers were negative. Cardiac magnetic resonance imaging was waived because the clinical conditions were rapidly deteriorating. Indeed, the patient was transferred for urgent cardiac surgery. The excised mass was 5 cm x 3.5 cm large and adherent to the right atrial roof, 1 cm close to the atrioventricular node. It was completely removed by the cardiac surgeon (Figure 2). The subsequent journey was regular, without complications. The histologic exam revealed that the mass was a giant myxoma (Figure 3). At follow–up the patient persisted asymptomatic. Figure 1. Transthoracic echocardiography. Figure 2. The excised right atrial mass. Figure 3. Histologic examination of the right atrial mass.