Introduction: Diagnosis of pheochromocytoma/paraganglioma (PPGL) can be challenging. Plasma metanephrines have highest sensitivity (96-99%) yet lowest specificity (85%)1 whereas 24-hour urinary metanephrines have 87.5% sensitivity and 99.7% specificity. Diagnostic accuracy depends on factors such as patient positioning and medications, questioning its potential value in a hospital setting. Methods: The audit was performed in a hospital which caters to a population of 400,000. Data was collected retrospectively on patients who had a request for plasma or urine metanephrines from March 2018 – September 2018. Results: A total of 85 patient order requests (58% male, 42% female) were reviewed; only 2 patients were ultimately diagnosed with a pheochromocytoma. The mean age of patients was 48 years. The most common indication for requests was hypertension (64 patients). Locations of order requests included 42% from outpatient clinics, 32% inpatient requests, 18% from Ambulatory Care, 6% by A&E and 2% by GP. Of the 27 (32%) inpatient requests, 10 had positive results: 1 diagnosed with primary aldosteronism, 1 with hypercortisolism and the others had no definite diagnosis. 8/10 patients with positive results did not have a repeat test. Focusing on plasma metanephrines, 52% plasma metanephrines samples were negative, 22% were positive and 26% were not processed due to laboratory error. From the 19 positive plasma metanephrines, adrenal adenoma was present in 7 patients (from this group, 1 was referred for surgery with confirmed diagnosis of pheochromocytoma), 1 patient’s MIBG scan was negative and 1 diagnosis of stress-related raised metanephrines was made. The remaining 10 patients did not undergo an adrenal scan. 9 out of 18 cases with positive urine metanephrines had an adrenal adenoma. In 7/9, plasma metanephrines were positive, the remaining 2 had negative plasma metanephrines. 34 cases with initial negative test still had another urine/plasma metanephrines performed with similar negative result. Furthermore <50% of the positive urine or plasma metanephrines were referred to and reviewed by the Endocrine team. Discussion: This audit highlights the potential pitfalls of investigating PPGL with plasma and urinary metanephrines, and in fact raises the question of its accuracy as an inpatient diagnostic tool as none of the positive inpatient tests resulted in a diagnosis of PPGL. Inappropriate urine and plasma metanephrines requests cause financial burden and patient anxiety. Even with outpatient requests, few positive results led to a PPGL diagnosis. Patient selection and conditions of testing must be more rigorously scrutinised and threshold for positive result must be raised for specificity of the test to be improved in ‘real world’ conditions. References: 1. Lenders JW al. Biochemical diagnosis of pheochromocytoma: which test is best? JAMA. 2002.
Urinary tract infections (UTIs) caused by antibiotic-resistant Gram-negative bacteria are a growing concern due to limited therapeutic options. Gram-negative bacteria, specifically Enterobacteriaceae, are common causes of both community-acquired and hospital acquired UTIs. These organisms can acquire genes that encode for multiple antibiotic resistance mechanisms, including extended-spectrum-lactamases (ESBLs), AmpC-β-lactamase, and carbapenems. The assessment of suspected UTI includes identification of characteristic symptoms or signs, urinalysis, dipstick or microscopic tests, and urine culture if indicated. UTIs are categorized according to location (upper versus lower urinary tract) and severity (uncomplicated versus complicated). Increasing rates of antibiotic resistance necessitate judicious use of antibiotics through the application of antimicrobial stewardship principles. Knowledge of the common causative pathogens of UTIs including local susceptibility patterns are essential in determining appropriate empiric therapy. The recommended first-line empiric therapies for acute uncomplicated bacterial cystitis in otherwise healthy adult nonpregnant females is a 5-day course of nitrofurantoin or a 3-g single dose of Fosfomycin tromethamine. Second-line options include fluoroquinolones and β-lactams, such as amoxicillinclavulanate. Current treatment options for UTIs due to AmpC-β-lactamase-producing organisms include Fosfomycin, nitrofurantoin, fluoroquinolones, cefepime, piperacillin-tazobactam and carbapenems. In addition, treatment options for UTIs due to ESBLs-producing Enterobacteriaceae include nitrofurantoin, Fosfomycin, fluoroquinolones, cefoxitin, piperacillin-tazobactam, carbapenems, ceftazidime-avibactam, ceftolozane-tazobactam, and aminoglycosides. Based on identification and susceptibility results, alternatives to carbapenems may be used to treat mild-moderate UTIs caused by ESBL-producing Enterobacteriaceae. Ceftazidime-avibactam, colistin, polymyxin B, Fosfomycin, aztreonam, aminoglycosides, and tigecycline are treatment options for UTIs caused by carbapenem-resistant Enterobacteriaceae (CRE). Treatment options for UTIs caused by multidrug resistant (MDR)-Pseudomonas spp. include fluoroquinolones, ceftazidime, cefepime, piperacillin-tazobactam, carbapenems, aminoglycosides, colistin, ceftazidime-avibactam, and cefdaloxime-tazobactam. The use of fluoroquinolones for empiric treatment of UTIs should be restricted due to increased rates of resistance. Aminoglycosides, colistin, and tigecycline are considered alternatives in the setting of MDR Gram-negative infections in patients with limited therapeutic options.
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