Tacrolimus metabolite cross-reactivity in different tacrolimus assays

Objectives: Tacrolimus (FK506) is an immunosuppressive drug with great clinical promise. There is a controversy regarding the role of tacrolimus metabolites in immunosuppression and toxicity, and immunoassays and immunophilin binding assays have not been adequately tested for metabolite cross-reactivity. Methods are limited to HPLC and HPLC-MS for quantifying the parent drug. Mixed lymphocyte culture assay (MLC) is the preferred functional bioassay for the measurement of parent drug and active metabolites but it is not practical for routine laboratory use. Due to differences in assay methods and reagent specificity, the concentration of tacrolimus in a given specimen may vary among different assay kit manufacturers. The objective of this study was to evaluate the degree of cross-reactivity or interference of the three first-generation tacrolimus metabolites [13-O-demethyl (M-I), 31-O-demethyl (M-II) and 15-O-demethyl (M-III)] among two different tacrolimus immunoassays (Immunoassay: PRO-Trac II FK506, Abbott IMx tacrolimus-II); and the radioreceptor assays (RRA) using minor immunophilins (14, 37, and 52 kDa immunophilins) and tacrolimus binding protein (FKBP12).

Methods: First-generation tacrolimus metabolites (M-I, M-II, and M-III) spiked in drug-free whole blood were assayed with RRA using three minor immunophilins (14, 37, and 52 kDa) and two commercial immunoassay procedures (Incstar PRO-Trac II tacrolimus, Abbott IMx tacrolimus II). The results were compared to previously published FKBP-12 RRA data and their immunosuppressive potency.

Results and conclusion: The first generation tacrolimus metabolites (M-I, M-II, and M-III) were tested using concentrations of 10 and 20 ng/mL. The significance of the metabolite interference (% of the total interference) was calculated based on the relative concentration of each metabolite present at steady-state trough concentrations in renal transplant recipients [22]. Metabolite I, which has no functional immunosuppressive activity showed minimal interference compared to M-II and M-III in all assays except the 14 kDa RRA. The Incstar PRO-Trac II tacrolimus assay showed the least M-I interference. Metabolite-II, which has a pharmacologic potency similar to the parent drug, showed a significant interference in the immunoassays and significant interference in radioreceptor assays. Metabolite III, which is pharmacologically inactive, produces 3–10% interference in the different assays if its presence in the blood is 6% of the parent drug. The total interference from these three metabolites was greater in the immunoassays than in the receptor assays. Receptor assays for tacrolimus provide results closer to the target value than do immunoassays.     

A multicenter clinical trial of gadolite oral suspension as a contrast agent for MRI

The purpose of this study was to assess the effectiveness and safety of Gadolite Oral Suspension as a gastrointestinal (GI) contrast agent for MRI in a phase II and two phase III multicenter clinical trials. Gadolite was administered to 306 patients with known or suspected abdominal and/or pelvic disease. MRI with T1- and T2-weighted sequences was performed before and after ingestion. Efficacy was evaluated by having two masked readers rate the certainty of their MR diagnosis (0 = uncertain, 1 = probable, 2 = definite) on randomly presented pre- and post-Gadolite Oral Suspension enhanced images. Principal investigators also evaluated the images and established the final diagnosis. Vital signs, clinical chemistries, and adverse events were documented. Blood and urine samples were analyzed for gadolinium content to determine whether Gadolite Oral Suspension was absorbed systemically. Certainty in MR diagnosis increased significantly (P < .001) for both blinded readers between pre- and post-Gadolite images (.49–1.18 for reader 1; .46–1.53 for reader 2). Sensitivity, specificity, and accuracy also increased for both masked readers. No gadolinium was detected in blood or urine samples. There were no serious adverse events and no apparent drug-related trends in mean vital signs or laboratory values. Gadolite is a highly effective, safe, and well tolerated contrast agent for clinical use with MRI.     

Cervical Cancer with Paraaortic Metastases: Significance of Residual Paraaortic Disease after Surgical Staging

Cervical carcinoma frequently metastasizes to the paraaortic region, necessitating extended field radiotherapy to effect a cure. As imaging modalities are unreliable in identifying all cases of paraaortic nodal metastases (PAN), surgical staging is often utilized prior to radiotherapy. This study was aimed at identifying factors predictive of survival in women with cervical carcinoma and paraaortic metastases. In particular, survival based on extent of paraaortic disease was examined. The study group consisted of 43 women (stages IB–IVB) identified between 1982 and 1993 who were treated with extended field radiation for cervical carcinoma with histologically confirmed paraaortic metastases. The estimated 5-year survival for the study population was 24% with a median survival of 18 months. Pelvic tumor size had a significant impact on survival with the median survival being 34 months if the primary lesion was <6 cm compared to 14 months if ≥6 cm (P= 0.01). Eight of the 26 (31%) women without residual PAN disease after surgical staging remain alive and disease free (mean follow-up, 74 months). In contrast, only 1 of the 17 (6%) women with gross residual PAN is alive 71 months after treatment (P= 0.05). However, a comparison of Kaplan–Meier survival curves did not show a statistically significant advantage to the surgical excision of grossly involved PAN (P= 0.98). Although long-term survival among women with grossly involved, unresected paraaortic metastases is uncommon, further study is necessary to elucidate the role of surgical excision of bulky aortic disease in women with cervical cancer.     

Acute inflammatory demyelinating polyradiculoneuropathy following varicella

Four cases of acute inflammatory demyelinating polyradiculoneuropathy following varicella are described. The role of immunosuppression as a contributing factor in triggering an autoimmune disease of the peripheral nervous system following viral infection is discussed.     

Cattle mortality in the Thane district, India: A study of cause/effect relationships

An unexpected mortality of more than 300 cattle was investigated near a metal recovery factory located in a rural area of the Thane district of India. The factory was engaged in reclaiming lead, aluminium, tin, and zinc from discarded lead storage batteries and soft drink cans. The environmental samples (soil, leaves, grass, slag, water, and sediment), human blood and hair and animal samples (blood, urine, peritoneal fluid, liver, kidney, cow dung, ribs, and femur), collected for analysis revealed toxic levels of lead, cadmium, and chromium. Clinical examination of factory workers and school children revealed cough, fever, gastric problems, abdominal pain, skin lesions (scabies), and blue line on gums. Histopathological examination of animal tissues revealed chronic pathology with lead inclusion bodies in hepatocytes and renal tubules. Based on environmental, clinical, analytical, and histopathological observations, the mortality has been attributed to toxic levels of metals in the body and the malnourished status of the animals.     

Sex difference in age at onset of schizophrenia: discrepant findings from India

Consecutive male (n=100) and female (n= 100) DSM-IV schizophrenics newly registered for treatment in a large psychiatric hospital were examined with regard to age at onset of the first psychotic symptom. Age at onset of the first psychotic symptom did not differ between the sexes regardless of whether schizophrenia was diagnosed by DSM-IV or by several alternative systems. Age at onset defined by other criteria, namely age at first contact with a physician, and age at first admission for psychiatric care, also did not show any differences between the sexes. Survival analysis of subjects having a documented date of birth revealed a female preponderance at younger ages. A higher positive symptom score predicted older age at onset of the first psychotic symptom in the total sample. These findings call into question the universality of the traditional view of a younger age at onset of schizophrenia among males. Tentative neurodevelopmental and cultural explanations are presented to explain why there is no sex difference in age at onset of schizophrenia in India.     

Endotracheal suctioning causes right upper lobe collapse in intubated children

Objective: Right upper lobe collapse is a common radiographic finding in intubated children. We hypothesized that deep suctioning and uncontrolled negative pressures during endotracheal tube suctioning were significant contributory factors. Methods : The incidence of right upper lobe (RUL) collapse in intubated, ventilated children on a paediatric cardiac intensive care unit was determined over a 3-month period ( n = 102). Graduated suction catheters and suction vacuums of < 165 cm H₂O were then introduced. Another prospective audit was carried out 3 months later ( n = 60). Results : We found that 24% developed RUL collapse and 4 developed an apical pneumothorax. Following the introduction of graduated catheters and controlled vacuums pressures, a significant reduction in the incidence of RUL collapse, to 7%, was observed ( p < 0.05). Conclusions : We conclude that high negative pressure and deep-suctioning causes RUL collapse in children. Any lobar collapse not only prolongs the child's stay in intensive care, but can be associated with further morbidity which may have a serious implication. By improving suctioning technique this morbidity can be significantly reduced.     

Leukemoid reaction: a diagnostic clue in metastatic carcinoma mimicking classic Hodgkin lymphoma

We report on 2 patients who were initially suspected to have classic Hodgkin lymphoma because of lymphadenopathy and the presence of Reed-Sternberg-like cells. Both patients had an associated leukemoid reaction (using a threshold leukocyte count of 50 000/microL) and were eventually diagnosed with metastatic carcinoma. Disseminated carcinoma can mimic Hodgkin lymphoma clinically, radiologically, and histologically. Reed-Sternberg-like cells may be found in carcinomas, and they represent a particularly challenging diagnostic pitfall for the unwary. When these cells lead to a suspicion of Hodgkin lymphoma, the presence of a leukemoid reaction should prompt the pathologist to question the diagnosis. Misdiagnosis can be avoided by the use of cytokeratin whenever a leukemoid reaction is present in a suspected case of Hodgkin lymphoma.