Deciding Which HIV Patients Need a Head CT
Deciding Which HIV Patients Need a Head CT
abstract & commentary
Source: Rothman RE, et al. A decision guideline for emergency department utilization of noncontrast head computed tomography in HIV-infected patients. Acad Emerg Med 1999; 6:1010-1019.
Hiv-infected patients are at risk for a wide range of clinically significant neurologic syndromes, some of which may be life-threatening. In an attempt to determine if specific clinical presentations are associated with new central nervous system (CNS) space-occupying lesions in HIV-infected patients with neurologic complaints, Rothman and colleagues performed a prospective convenience sample study of such patients presenting to an inner-city ED over an 11-month period. A standardized evaluation was used to ascertain the development of new neurologic signs and symptoms. All patients with new findings underwent noncontrast head computerized tomography (CT) scans. Variables independently associated with new focal findings on head CT scans were incorporated into a decision guideline.
One hundred ten patients were found to have new neurologic findings and underwent head CT scans. Twenty-seven patients (24%) had focal lesions on head CT, 19 (18%) of which were new. Mass effect was noted in eight of these patients. Factors independently associated with new focal lesions included new seizure (RR = 73.5, 95% CI = 6.2-873.0) and different quality headache (RR = 27.0, 95% CI = 3.2-230.1). Using these factors as a screening tool would have identified 18 of 19 patients (95%) with new focal lesions, and would have yielded a 53% reduction in head CT scans. Including prolonged headache of at least three days’ duration would have identified all patients and yielded a 37% reduction in head CT scans. A full 74% of patients with new focal CNS lesions required emergent therapy. Rothman et al conclude that specific clinical findings are associated with new focal CNS lesions in HIV-infected patients. If prospective validation of these guidelines occurs, significant and safe limitation of the use of emergent head CT scans in this group of patients could occur.
Comment by Frederic Kauffman, MD, FACEP
This is an extremely well-designed study. The patient population studied was an undifferentiated group of HIV-positive patients with neurologic complaints; the design was prospective; the decision to obtain a head CT scan could not be overridden by other physicians; the neurologic questionnaire/data sheet assessed all pertinent signs and symptoms; and 100% of the forms were filled out prior to ordering CT scans. CD4 counts within the prior 12 months were available for analysis in 95% of patients, and other emergent care was not delayed as a result of the study. The fact that 74% of patients with new focal lesions required emergent therapy highlights the importance of sound, validated decision guidelines. In addition, it should be emphasized that the lack of focal neurologic findings on clinical exam does not rule out the presence of a new focal lesion (58% of patients in this study with new focal lesions had no focal neurologic findings in the ED). I admit to being surprised that contrast CT scanning was not performed in this study. In view of the fact that disorders such as CNS toxoplasmosis are common in the HIV-infected population, my practice has always been to include contrast evaluation in patients in whom CNS pathology is suspected. Rothman et al are unaware, however, of any patients at their institution over the past 10 years in whom emergent therapy was delayed due to the lack of contrast on initial CT scan, though they readily admit that definitive diagnosis may subsequently require the use of contrast CT or MRI techniques.
This study is a large first step in better understanding the role of emergent neuroimaging in HIV-infected patients. Prospective evaluation of the proposed clinical guidelines is in order before widespread adoption in daily ED practice. Certainly, however, every HIV-infected patient with a new seizure, depressed or altered orientation, or different or prolonged headache must receive emergent neuroimaging. Future studies will determine the necessity of contrast enhancement and the role of MRI vs. CT in ED patients.
HIV-positive patients need neuroimaging (CT or MRI) if:
a. they have a fever.
b. they have a new seizure.
c. they have a CD4 count < 500.
d. they are being admitted to the hospital.
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