Search

We report a case of a false-positive HIV result in an apparently healthy pregnant woman. Since no prenatal HIV testing had been performed, we screened for HIV reactivity utilizing the Architect HIV-Ag/Ab Combo assay. Results obtained were inconsistent in that they were repeatedly HIV reactive on a single serum sample while nonreactive on a plasma sample. However, both sample types were nonreactive on the Advia Centaur HIV-1/O/2 and Oraquick assays. For further confirmation, an HIV-1 Western blot and viral load were performed; blot results were indeterminate while the viral load was undetectable. We concluded that the repeatedly reactive serum serology results were false-positive. While the cause of this false reactivity is not clear, most likely fibrin microclots in the serum sample interfered with the assay and thus accounted for the false positivity. Plasma may thus provide a more appropriate sample type when using the Architect assay, especially when testing pregnant women.

Phenytoin is a commonly used anticonvulsant that is highly protein bound with a narrow therapeutic range. The unbound fraction, free phenytoin (FP), is responsible for pharmacologic effects; therefore, it is essential to measure both FP and total serum phenytoin levels. Historically, the Abbott TDx method has been widely used for the measurement of FP and was the method used in our laboratory. However, the FP TDx assay was recently discontinued by the manufacturer, so we had to develop an alternative methodology. We evaluated the Beckman-Coulter DxC800 based FP method for linearity, analytical sensitivity, and precision. The analytical measurement range of the method was 0.41 to 5.30 microg/mL. Within-run and between-run precision studies yielded CVs of 3.8% and 5.5%, respectively. The method compared favorably with the TDx method, yielding the following regression equation: DxC800 = 0.9**TDx + 0.10; r2 = 0.97 (n = 97). The new FP assay appears to be an acceptable alternative to the TDx method.

The immediate post-HIV testing world of blood banking was a challenging time.1 Public concerns over blood safety fueled a tremendously powerful dynamic within the community to adopt testing and screening measures to deal with progressively more remote risks of transfusion-transmitted illnesses. Indeed, it was reasonable for patients to expect to receive untainted blood products in our hospitals. The result of this dynamic is now a safety profile for transfusion that begins to approach that of other low-risk activities of daily living, such as driving to the store or flying on a major airline.1,2 The firestorm of discussion and debate over each new risk, test, or screening method during the height of that era created a workable process by which to engage in this discussion, and has made the community keenly aware of the need to monitor for new risks. We are now generally more able to decide how, when, or if we should implement additional testing or screening measures to deal with those risks. That is not to say that this has come without considerable and even continuing controversy, but it has brought both the public and providers together to engage on the matter of expectations.1 The lessons learned from this era in blood banking should be studied and carefully considered as scrutiny of other aspects of medical care, and in particular laboratory testing and its risks (safety issues), come to light. Best practices, whether they are business models, software, or hardware tools, will rapidly become the standard of care, driven by a combination of legal, liability, regulatory, public perception, and payer pressures. Just as there was a race to adopt HIV antigen and then nucleic acid based testing (NAT) in the blood banking industry, there must be a rush to adopt a host of …

Patient: 52-year-old Caucasian male. Chief Complaint: Increasing fatigue and weakness. History of Present Illness: Our patient presented for evaluation of an acute worsening of progressive weakness over the past month. He felt so weak that he almost “passed out.” He also reported an increased fluid intake and an increase in urinary output. There was no pain on urination or history of urinary tract infection. He denied chest pain, vision problems, nausea, diarrhea, and syncope. Family members were concerned that the patient was “wobbly” when he walked. While waiting in the emergency room, the patient experienced 2 tonic-clonic seizures. Past Medical History: Nephrolithiasis, hypertension, benign prostatic hypertrophy. Medication History: Lisinopril, potassium, Allopurinol, Flexeril. Social History: Denies alcohol and tobacco use. Physical Exam Findings: Blood pressure, 71/36 mm Hg; pulse, 115; respiratory rate, 22; and temperature, 36.9°C. The patient was awake and responsive but not oriented. The skin was dry and turgor was poor. The oral mucosa was also dry. The abdominal exam revealed mid-epigastric tenderness. Neurologic exam was nonfocal. Lung and cardiac exams were normal. Principal Laboratory Findings: Tables 1, 2, 3, 4 , and 5 . 1. What are this patient’s most striking clinical and laboratory test findings? 2. How do you explain these findings? 3. What is your differential diagnosis? 4. What additional laboratory test would be useful in confirming the diagnosis of this patient’s condition? 5. What laboratory tests might explain the precipitating event which caused this patient’s condition? 6. What is the most likely diagnosis? 7. What is the treatment and management of this disorder? 1. This patient has several important critical signs and symptoms that include seizure, lethargy, polydipsia, polyuria, hypotension, epigastric pain, and tachycardia. The …