Hyperprolactinemia in antipsychotic-naive patients with first-episode psychosis

BACKGROUND

Hyperprolactinemia is frequent in patients with schizophrenic psychoses. It is usually regarded as an adverse effect of antipsychotics but has recently also been shown in patients without antipsychotic medication. Our objective was to test whether hyperprolactinemia occurs in antipsychotic-naive first-episode patients (FEPs).

METHOD

In the framework of the European First Episode Schizophrenia Trial (EUFEST), 249 out of 498 FEPs were eligible for this study, of whom 74 were antipsychotic naive. All patients were investigated regarding their serum prolactin levels with immunoassays standardized against the 3rd International Reference Standard 84/500.

RESULTS

Twenty-nine (39%) of the 74 antipsychotic-naive patients showed hyperprolactinemia not explained by any other reason, 11 (50%) of 22 women and 18 (35%) of 52 men.

CONCLUSIONS

Hyperprolactinemia may be present in patients with schizophrenic psychoses independent of antipsychotic medication. It might be stress induced. As enhanced prolactin can increase dopamine release through a feedback mechanism, this could contribute to explaining how stress can trigger the outbreak of psychosis.

European proficiency study with control serum for the tumor marker CA 19-9 measured on different test systems

BACKGROUND

Reliable and precise CA 19-9 testing is required for the long-term follow-up of patients with pancreatic carcinoma during therapy. The aim of this longitudinal proficiency study was to evaluate the comparability, linearity, and precision of CA 19-9 determinations performed in different laboratories using currently available test systems under routine conditions.

METHODS

During the one year study period, 15 laboratories applied 7 different tests and included a liquid BIOREF control serum with pancreatic carcinoma derived CA 19-9 in their routine testing and quality control procedures. The results were collected centrally and evaluated statistically.

RESULTS

The comparability of CA 19-9 results is limited especially when different tests are used, albeit, some tests show a good correlation: The CA 19-9 values obtained by different laboratories using different test systems vary up to a factor of 2. The precision of CA 19-9 determinations was acceptable in most laboratories with coefficients of variation ranging between very low 3.2% and high 17.8%. The imprecision was slightly increased when automatic dilution procedures of the analysers were used.

CONCLUSIONS

The comparability of CA 19-9 test results must be improved. The precision is acceptable in most cases. In order to monitor key performance parameters, every laboratory should participate in external quality assessment schemes and should perform a routine internal quality control with a control serum independent from the test kit manufacturer.

Multicenter analytical evaluation of a high-sensitivity troponin T assay

BACKGROUND

High-sensitivity cardiac troponin assays are being introduced clinically for earlier diagnosis of acute myocardial infarction (AMI). We evaluated the analytical performance of a high-sensitivity cardiac troponin T assay (hscTnT, Roche Diagnostics) in a multicenter, international trial.

METHODS

Three US and 5 European sites evaluated hscTnT on the Modular® Analytics E170, cobas® 6000, Elecsys 2010, and cobas® e 411. Precision, accuracy, reportable range, an inter-laboratory comparison trial, and the 99th percentile of a reference population were assessed.

RESULTS

Total imprecision (CVs) were 4.6-36.8% between 3.4 and 10.3 ng/L hscTnT. Assay linearity was up to 10,000 ng/L and the limit of blank and detection were 3 and 5 ng/L, respectively. The 99th percentile reference limit was 14.2 ng/L (n=533). No significant differences between specimen types, assay incubation time, or reagent lots existed. A substantial positive bias (76%) exists between the 4th generation and hscTnT assays at the low end of the measuring range (<50 ng/L). hscTnT serum pool concentrations were within 2SD limits of the mean of means in the comparison trial, indicating comparable results across multiple platforms and laboratories.

CONCLUSION

The Roche hscTnT assay conforms to guideline precision requirements and will likely identify additional patients with myocardial injury suspicious for AMI.

The prevalence of aminoglycoside resistance and corresponding resistance genes in clinical isolates of staphylococci from 19 European hospitals

Aminoglycosides still play an important role in antistaphylococcal therapies, although emerging resistance amongst staphylococci is widespread. To further our understanding of the prevalence of aminoglycoside resistance in Europe, we tested 699 and 249 consecutive unrelated clinical isolates of Staphylococcus aureus and coagulase-negative staphylococci (CNS), respectively, from the SENTRY Antimicrobial Surveillance Program, for susceptibility to gentamicin, tobramycin, kanamycin and streptomycin, and examined the relationship between susceptibility to these antimicrobials and susceptibility to methicillin. Three hundred and sixty-three staphylococcal isolates demonstrated resistance to at least one of the aminoglycosides tested; all of these isolates were screened for the presence of aac(6')-Ie + aph(2"), ant(4')-Ia and aph(3')-IIIa, the genes encoding the most clinically relevant aminoglycoside-modifying enzymes. S. aureus isolates derived from hospital-acquired pneumonia tended to be more resistant to aminoglycosides and methicillin than isolates from blood or wound infections. In S. aureus, resistance to aminoglycosides was closely associated with methicillin resistance. Susceptibility of S. aureus to gentamicin has decreased by 9% from previous European studies to a current level of 77%, while susceptibility of CNS, currently at 67%, has increased by 21%. Geographical variation occurred, correlating with methicillin resistance, although intra-country variation was considerable. aac(6')-Ie + aph(2"), ant(4')-Ia and aph(3')-IIIa were found throughout Europe in 68%, 48% and 14% respectively of staphylococci resistant to at least one aminoglycoside. aph(3')-IIIa was considerably more common in methicillin-susceptible S. aureus and CNS isolates; the reverse was true for the other two resistance genes. The prevalence of ant(4')-Ia and aph(3')-IIIa genes in aminoglycoside-resistant staphylococci was significantly greater than that reported in previous European studies.

Optimized determination of angiotensin I-converting enzyme activity with hippuryl-L-histidyl-L-leucine as substrate

The determination of the angiotensin I-converting enzyme activity (ACE, kininase II, peptidyldipeptide hydrolase, EC 3.4.15.1) is necessary to control the course and the treatment of sarcoidosis, as well as to monitor the therapeutic use of enzyme inhibitors such as captopril in hypertension or congestive heart failure. Numerous synthetic substrates are known with which to measure the enzyme activity. A discontinuous method using hippuryl-L-histidyl-L-leucine was tested and improved. The cleavage product, hippurate, reacts with cyanuric chloride to give a yellow complex which can be measured at 405 nm using a spectral line photometer. Enzyme activity, kinetic constants and activation energy are dependent on the chloride ion concentration. Optimal test concentrations are 1.1 mol/l potassium chloride and 3.0 mmol/l hippuryl-L-histidyl-L-leucine at pH 8.3. Higher substrate concentrations effect an inhibition of the enzyme reaction. A Michaelis constant of 0.9 mmol/l was found with serum as enzyme source. An activation energy of 57 kJ/mol was obtained from the relation between the logarithm of velocity of enzyme reaction and reciprocal value of absolute temperature. Furthermore, a linear dependence on chloride ion concentration was observed. The histogram of the enzyme activities in sera from 146 healthy volunteers shows a non-gaussian distribution. The reference interval at 25 degrees C is characterized by a median of 24 units/l with the 2.5th and the 97.5th percentiles at 13 units/l and 42 units/l, respectively. The corresponding values at 37 degrees C are 27 units/l and 86 units/l with a median of 48 units/l. No significant sex and age dependence could be found. A potent ACE inhibitor such as captopril leads to a rapid decrease of the enzyme activity within 60 min after oral administration. In the following hours, the enzyme activity slowly increases.

Efficacy of transferrin determination in human sera in the diagnosis of iron deficiency

Apparently healthy persons (n = 425) as well as 264 patients characterized by an iron concentration in serum < 7.2 mumol/l were examined. A latent iron deficiency was defined as a concentration of ferritin < 20 micrograms/l (males) and < 15 micrograms/l (females), without anaemia; manifest iron deficiency defined by an additional presence of hypochromic microcytic anaemia. Fifty-nine of 425 (= 14%) apparently healthy persons showed a latent iron deficiency. In the remaining 366 we established the following reference intervals for the concentration of transferrin in serum [mumol/l]: 25.2-45.3 (males), 29.1-54.5 (females, < or = 25 years of age) and 25.3-48.6 (females, > 25 years of age). Eight of 59 (= 14%) apparently healthy persons with latent iron deficiency had a transferrin concentration above the reference interval. Sixty-one of 264 (= 23%) patients with an iron concentration < 7.2 mumol/l showed a ferritin concentration < 20 micrograms/l (males) and < 15 micrograms/l (females). Thirty-eight of these 61 patients (= 62%) had a manifest iron deficiency. In 18 of these 38 patients (= 47%) the transferrin concentration was increased. For our 264 patients we determined the diagnostic validity of an increased transferrin concentration for diagnosis of iron deficiency, assuming an iron deficiency if the concentration of ferritin remained below the discrimination values mentioned above: The diagnostic sensitivity was 36%, the diagnostic specificity 97%, the predictive value of the positive test result 79% and the predictive value of the negative test result 83%.(ABSTRACT TRUNCATED AT 250 WORDS)