To test whether academic centers (ACs) are more successful than nonacademic centers (NACs) in immunohistochemistry (IHC) external quality assessment challenges in the Canadian Immunohistochemistry Quality Control (CIQC) program.
Results of 9 CIQC challenges for breast cancer marker (BM) and various non-breast cancer marker (NBM) tests were examined. Success rates were compared between AC/NAC laboratories and those located in small or large cities. Performance was also correlated with annual IHC case volumes.
There was no statistically significant difference in performance in any of the comparisons. However, overall performance on BM was significantly better (P
Pyrazinamide (PZA) is a key drug in the treatment of tuberculosis (TB), including multidrug-resistant TB. Drug susceptibility testing (DST) of Mycobacterium tuberculosis against PZA is not included in the World Health Organization's yearly proficiency testing. There is an increasing need to establish quality control of PZA DST.
To evaluate the performance of PZA DST and to introduce a quality assurance system for the test in Sweden.
Panels with PZA-susceptible and -resistant isolates were used in three rounds of proficiency testing in all five Swedish clinical TB laboratories and our reference laboratory. All laboratories used the MGIT 960 system. Minimum inhibitory concentrations (MICs) were determined and the pncA gene was sequenced to further characterise the 52 panel strains.
Good agreement was seen between the phenotypic PZA DST and pncA sequence data, and MIC determination confirmed high levels of resistance. However, in contrast to other drugs, for which correct proficiency test results were observed, specificity problems occurred for PZA DST in some laboratories.
In Sweden, using panel testing, differences were seen in the proficiency of TB laboratories in correctly identifying PZA susceptibility. Improved results were noted in the third round; PZA has therefore been included in yearly proficiency testing.
Serum lithium is monitored to ensure levels within the narrow therapeutic window. This study examines the interlaboratory variation and inaccuracy of lithium monitoring in Denmark.
In 16 samples consisting of (1) control materials (n = 4), (2) pooled patient serum (n = 5), and (3) serum from individual patients (n = 7), lithium was measured in 19 laboratories using 20 different instruments. The lithium concentrations were targeted by a reference laboratory. Ion-selective electrode (n = 5), reflective spectrophotometric (RSM, n = 5), and spectrophotometric (n = 10) methods were used.
Acceptable accuracy-interpreted as total differences from target values (bias) less than or equal to ±12%-was generally found in patient samples above 0.7 mmol/L. Below 0.7 mmol/L, 8 instruments had 2 or more patient samples exceeding a difference to the targeted reference value of >12%. Seven of these instruments had a systematic positive or negative bias and more so at lower lithium concentrations. Three poorly calibrated instruments were found in the ion-selective electrode group, 3 in the spectrophotometric group, and 2 in the RSM group. The instruments using reflectance spectrophotometry (RSM) were on average 21% positively biased when measuring control materials. However, this effect was not observed in patient samples.
Large interlaboratory variation was found below 0.7 mmol/L because of 7 instruments with a poor accuracy and 1 with poor precision. Methods should be recalibrated or substituted. Controls below 0.7 mmol/L are recommended.