Further Thoughts on the Diagnosis and Diagnostic Criteria for Thyroid Storm

Abstract

Thyroid storm is a rare condition with a high mortality rate. Even if diagnosed early, death can occur, and reported mortality rates have ranged from 2% to 75% in hospitalized patients (1–3). Most immediate causes of death from fulminant thyrotoxicosis have been described as sudden cardiovascular collapse, with shock and arrhythmias including ventricular fibrillation. The cases have usually been described as resistant to all the usual resuscitative efforts (4). An accurate estimation of the incidence of thyroid storm is impossible to determine because of the considerable variability in the criteria for its diagnosis. Furthermore, prospective studies are impossible to conduct in a disease of such rarity on the one hand and acute occurrence on the other. With the available current therapeutic resources, death from thyrotoxicosis or from its treatment should be rare, and thyroid storm does indeed appear to be occurring less frequently today than in the past. This is most likely due to more widespread information among physicians and the general population on thyroid diseases in general and thyrotoxicosis in particular, as well as better diagnostic instruments to ensure earlier diagnosis and treatment of thyrotoxicosis. This improved management would thus preclude progression of thyrotoxicosis to the crisis stage. Nevertheless, as described very recently, it may occur in 1% to 2% of hospital admissions for thyrotoxicosis (5), and must therefore still be considered one of the more important and prevalent endocrine emergencies. In the July 2012 issue of Thyroid, a landmark study by Akamizu et al. (6) described two stepwise national surveys of thyroid storm in Japan that looked at its incidence, diagnostic criteria, clinical features, mortality, and prevalence of survival with complications. The authors first developed diagnostic criteria based on 99 patients in the literature and seven of their own patients. Thyrotoxicosis was a prerequisite for both sets of diagnostic criteria. Additional criteria were a combination of classical features such as central nervous system manifestations, fever, tachycardia, congestive heart failure and gastrointestinal (GI)/hepatic disturbances. Similar parameters were also considered by Burch and Wartofsky (1). Using these criteria, Akamizu et al. (6) subsequently conducted two nationwide surveys from 2004 to 2008, targeting all hospitals in Japan. The purpose of the first survey was to identify cases of thyroid storm. The second survey was intended to obtain detailed clinical and laboratory information regarding these cases. It is important to note that the followup survey did not stop with obtaining the information provided in the forms filled out by the respondents. As a further step, the information was vetted and respondents were contacted to fill in gaps in the data. Ultimately, Akamizu et al. (6) identified 282 patients who were assigned the diagnosis of thyroid storm, grade 1 (TS1) and 74 patients who were assigned the diagnosis of thyroid storm, grade 2 (TS2). Readers should recognize that this terminology (i.e., TS1 and TS2) was developed after the authors completed the study. In developing the initial criteria for the diagnosis of thyroid storm, one that was based on a review of the literature, the authors formulated criteria for what they referred to as ‘‘definite thyroid storm’’ and ‘‘suspected thyroid storm.’’ This terminology was used in their surveys and data records. The results of the study were, however, at odds with ‘‘definite’’ and ‘‘suspected’’ as appropriate terminologies. Thus, based on the final diagnostic criteria for each of these categories, one can calculate that the mortality rate of suspected thyroid storm, 9.9%, was almost as high as the mortality rate of definite thyroid storm, 10.9%. Given these observations, and the fact that the mortality rate of thyrotoxic patients without thyroid storm was less than 1%,* it seemed better not to use ‘‘suspected’’ for a group that had such a high mortality. Hence the terminology TS1 and TS2 were used. In addition to developing their own diagnostic criteria, Akamizu et al. (6) assigned to the patients the scores for thyroid storm proposed by Burch and Wartofsky (1) based on their seminal review of the literature. They noted that median scores (ranges) of patients with TS1 was 70 points (15–120), and those of patients with TS2 was 52.5 (25–90) points. Patients fulfilling TS1 criteria thus had a more evident disease burden and were notable for the presence of neurological