Jae-Lim Choi

Platelet Function Tests: A Review of Progresses in Clinical Application

The major goal of traditional platelet function tests has been to screen and diagnose patients who present with bleeding problems. However, as the central role of platelets implicated in the etiology of arterial thrombotic diseases such as myocardial infarction and stroke became widely known, platelet function tests are now being promoted to monitor the efficacy of antiplatelet drugs and also to potentially identify patients at increased risk of thrombosis. Beyond hemostasis and thrombosis, an increasing number of studies indicate that platelets play an integral role in intercellular communication, are mediators of inflammation, and have immunomodulatory activity. As new potential biomarkers and technologies arrive at the horizon, platelet functions testing appears to take on a new aspect. This review article discusses currently available clinical application of platelet function tests, placing emphasis on essential characteristics.

Urinary Neutrophil Gelatinase-Associated Lipocalin Levels in Comparison with Glomerular Filtration Rate for Evaluation of Renal Function in Patients with Diabetic Chronic Kidney Disease

Background Neutrophil gelatinase-associated lipocalin (NGAL) is a promising biomarker of acute kidney injury. There is a growing body of evidence suggesting that NGAL is also a marker of kidney disease and severity in chronic kidney disease (CKD). We studied the utility of urinary NGAL in more accurately predicting renal function in patients with diabetic CKD. Methods We studied possible relationships between urinary NGAL, estimated glomerular filtration rate (eGFR), and proteinuria in diabetic CKD patients and in healthy populations. Results Urinary NGAL levels were significantly higher in CKD patients than in healthy controls (96.0 [2.7 to 975.2] ng/mL vs. 18.8 [1.3 to 81.9] ng/mL, P=0.02), and the GFR was lower among CKD patients (49.3 [13.1 to 78.3] mL/min/1.73 m2 vs. 85.6 [72 to 106.7] mL/min/1.73 m2, P<0.0001). The urinary NGAL level showed a significant inverse correlation with GFR (r=-0.5634, P<0.0001). The correlation analyses between urinary protein level and urinary NGAL levels and GFR were as follows: urine protein and urinary NGAL (r=0.3009, P=0.0256), urine protein and GFR (r=-0.6245, P<0.0001), urine microalbumin and urinary NGAL (r=0.1794, P=0.2275), and urine microalbumin and GFR (r=-0.5190, P=0.0002). Conclusion From these results, we concluded that urinary NGAL is a reliable marker of renal function in diabetic CKD patients. However, urinary NGAL did not provide more accurate information regarding renal function than GFR.

Clinical Usefulness of Serum Cystatin C as a Marker of Renal Function

Background Accurate renal function measurements are important in the diagnosis and treatment of kidney diseases. In contrast to creatinine, the production of serum cystatin C has been extensively reported to be unaffected by body muscle mass, age, gender, and nutritional status. Methods Our study included 37 samples from diabetic chronic kidney disease (CKD) patients for whom serum creatinine tests had been requested and 40 samples from a healthy populations in Dong-A University Hospital between May 2010 and June 2010. The assay precision (i.e., the coefficient of variation) and the reference range of the serum cystatin C test were evaluated. We compared the estimated glomerular filtration rates (GFRs) based on cystatin C with those based on creatinine. Moreover, we investigated the influences of age, gender, weight, and muscle mass on serum creatinine and serum cystatin C. Results There was a positive correlation between GFR based on creatinine and that based on cystatin C (r=0.79, P<0.0001) among the diabetic CKD patients. Serum creatinine and cystatin C were significantly correlated with body weight and muscle mass, but the strengths of these correlations were greater for serum creatinine. The precision study revealed excellent results for both the high and low controls. The 95% reference interval of cystatin C in the healthy population was 0.371 to 1.236 mg/L. Conclusion Based on these results, we conclude that, despite the strong correlation between serum creatinine and cystatin C, cystatin C is less affected by weight and muscle mass and might represent a better alternative for the assessment of renal function.

Outbreak of Pseudomonas Oryzihabitans Pseudobacteremia Related to Contaminated Equipment in an Emergency Room of a Tertiary Hospital in Korea

Pseudomonas oryzihabitans is frequently found in various sites within hospital settings, including sink drains and respiratory therapy equipment. Although it rarely causes human infections, P. oryzihabitans has recently been considered a potential nosocomial pathogen, especially in immunocompromised hosts. We report our experience of an outbreak of P. oryzihabitans pseudobacteremia, presumably due to faulty aseptic preparation of a saline gauze canister.

Neutrophil-to-Lymphocyte Ratio Is Associated with Impaired Interferon-Gamma Release to Phytohemagglutinin.

Objective The neutrophil-to-lymphocyte ratio (NLR) has been shown to predict adverse outcomes in several pathologic conditions. The majority of indeterminate interferon (IFN)-γ release assays were due to inadequate IFN-γ response to the phytohemagglutinin. We sought to study the value of NLR to predict an indeterminate result of QuantiFERON-TB Gold In-Tube (QFT-GIT) performed in routine laboratory practice. Methods Results from 2,773 QFT-GIT assays were analyzed. Data collection included demographic data, the level of IFN-γ to nil, mitogen, and TB antigen of QFT-GIT, total WBC, and a differential count. We calculated the absolute neutrophil count, lymphocyte count, and NLR. Results Of the total, 224 (8.1%) indeterminate results were observed. Twelve (1.8%) showed indeterminate results in the NLR range from 1.71 to 2.84, but 132 (19.2%) had indeterminate results in NLR≥5.18 (p<0.0001). The likelihood ratio for indeterminate results were 2.70 (95% CI, 2.36-3.08) in NLR ≥5.18 and 1.93 (95% CI, 1.64-2.27) in lymphocyte count ≤1050/μL. NLR and neutrophil count were independent predictors for indeterminate QFT-GIT result in multiple regression analysis. The IFN-γ response to PHA was negatively associated with NLR (r=-0.33, p<0.001). Conclusion We showed that the NLR is an independent predictor of indeterminate QFT-GIT result. Low frequency of indeterminate results in group with normal NLR may imply the importance of a balance between two cellular compartments in physiological and pathological conditions.

A case of Clostridium difficile bacteremia in a patient with loop ileostomy.

Clostridium difficile, an anaerobic, spore-forming, gram-positive, rod-shaped bacterium, is the most common nosocomial pathogen causing pseudomembranous colitis. C. difficile is not intrinsically invasive and rarely infects extraintestinal sites. The bacterium, therefore, is not commonly detected in blood cultures. Here, we report a case of C. difficile bacteremia in a patient who had underwent loop ileostomy because of rectal obstruction following metastatic colon cancer originated from prostate cancer.

Significance of interferon-gamma response to mitogen in serial QuantiFERON-TB Gold In-Tube assay of routine laboratory practice.

BACKGROUND Clinical data of serial interferon-γ release assay (IGRA) testing in routine laboratory practice are limited. IFN-γ response to mitogen is used as a positive control in IGRA. We assessed the association between IFN-γ response to nil, mitogen, tuberculosis (TB) mycobacterial antigens, and the variations from the results of the serial testing. METHOD A total of 299 patients with serial QuantiFERON-TB Gold In-Tube (QFT-GIT) were enrolled. The medical records of patients were reviewed for demographic information, status of Mycobacterium tuberculosis infection, treatment of tuberculosis, and the quantitative response to nil, mitogen, and TB antigen. RESULTS The initial QFT-GIT result was positive in 142 patients (47.5%), negative in 139 (46.5%), and indeterminate in 18 (6.0%). Of total, 79.6% showed concordant results in serial testing. The discordance in serial tests was significantly high in patients with a low mitogen response (≤ 3.93 IU/ml) (p<0.0001). Quantitative TB responses around the cut-off point in serial QFT-GIT were associated with an increased conversion and reversion rates (p = 0.01, p = 0.0005), respectively. CONCLUSION Because IGRAs are dynamic assays, integrated interpretation of quantitative TB response with mitogen and nil response would be helpful in serial QFT-GIT. Recommendations for the interpretation of results of serial testing for active TB will be required.

Association between the microarray-based CYP2C19 genotyping assay and the platelet function test in cardiovascular patients receiving clopidogrel.

Sir, Clopidogrel irreversibly inhibits platelet P2Y12 ADP receptors. It is a pro-drug and transformed into an active metabolite in the liver by cytochrome P450 (CYP), including CYP2C19. The CYP2C19 genetic polymorphism has been reported to associate with a variable response to Clopidogrel. It is suggested the loss-of-function allele, CYP2C19*2 and CYP2C19*3, correlate with reduced antiplatelet activity of clopidogrel, and the gain-of-function allele, CYP2C19*17, with an increased activity [1, 2]. All of these alleles represent considerable variation by race, and Asians show a higher frequency of loss-of-function allele and lower frequency of gain-of-function allele than other race [3, 4]. Therefore, it would be significant to evaluate the frequency of these alleles in Korean. In this study, we investigated the frequency of CYP2C19 alleles with the microarray-based genotyping and the association between the genotyping assay and the platelet function test. We also investigated the possibility of CYP2C19 genotyping as the marker of treatment effect and the assistant of treatment decision. A total of 155 patients diagnosed with acute coronary syndrome in the Dong-A University Hospital between April 2010 and August 2012 was evaluated. All patients underwent percutaneous coronary intervention and received dual therapy with aspirin and clopidogrel, which was given as a 300-mg loading dose and a 75-mg maintenance dose. The genotypes, P2Y12 reaction units (PRU), and percent inhibition results were all analyzed at the preprocedure/postprocedure time. The preprocedure time means the time at 4 h after loading dose, and the postprocedure time means the time at 24 h after maintenance dose started. This study was approved by the Institutional Review Board of Dong-A University Hospital. Informed consent was obtained from each patient, and blood samples were collected. CYP2C19 genotyping was performed by the Verigene system CLO+ test (Nanosphere, Northbrook, IL, USA). One milliliter fresh whole blood samples were used for test. Test cartridges added with samples were loaded into Verigene processor. The extraction of nucleic acid and hybridization were automatically performed by this processor. The result on the glass slide was analyzed by Verigene reader. Genotypes were categorized as ultra-rapid metabolizer (UM, including *17/*17 and *1/*17), extensive metabolizer (EM, including *1/*1), intermediate metabolizer (IM, including *1/*2 and *1/*3), and poor metabolizer (PM, including *2/*2, *3/*3 and *2/*3). The results were aligned with the results of the direct sequencing. The degree of platelet inhibition was assessed by the VerifyNow P2Y12 system (Accumetrics, San Diego, CA, USA). Blood samples were collected before and after the percutaneous coronary intervention. An assay was performed according to the manufacturer’s directions within 10–15 min of sampling. The results were expressed as P2Y12 reaction units (PRU) and percent inhibition. Although there is no consented cutoff value for PRU and percent inhibition, high PRU value (≥239) and low percent inhibition (≤10%) were regarded as clopidogrel resistance according to the manufacturers’ recommendations. Statistical analysis was performed using MedCalc version 9.3 (MedCalc Software, Belgium, Europe). The findings for the CYP2C19 subgroups were compared using the Chi-square and Kruskal–Wallis tests. P-values of <0.05 were regarded as significant. Four of 155 patients had have UM (2.6%), 56 EM (36.1%), 69 IM (44.5%), and 26 PM (16.8%) genotypes. Among the 155 patients, 95 (61.3%) were carriers for the CYP2C19*2 or CYP2C19*3. The percentage of the UM genotype group was too low to compare with the other groups, so we analyzed the EM, IM, and PM genotype groups and excluded the UM genotype group. There were no significant differences in the demographic and clinical findings between the CYP2C19 subgroups. The results of platelet function test in the genotyping subgroups are shown in Table 1 and Figure 1. The preprocedure PRU values of EM patients were significantly lower than those of IM and PM patients (P = 0.001), and the preprocedure/postprocedure percent inhibition values