Validation of three coding algorithms to identify patients with end-stage liver disease in an administrative database

PURPOSE: Use of administrative or population-based databases for post-marketing pharmacoepidemiology research in patients with end-stage liver disease (ESLD) has been limited by the difficulty of accurately identifying such patients. Algorithms to identify patients with ESLD using ICD-9-CM codes have not been developed outside of the Veterans Affairs healthcare setting. METHODS: We queried electronic medical records at two tertiary care hospitals to identify patients with ICD-9-CM codes indicative of ESLD. Coding algorithms were developed to identify patients with confirmed ESLD, and these were tested to determine their positive predictive value (PPV). RESULTS: The presence of one inpatient or outpatient ICD-9-CM code for: (i) cirrhosis; (ii) chronic liver disease, and (iii) a hepatic decompensation event yielded a PPV of 85.2% (167/196; 95% CI: 79.4%-89.9%). The PPV increased to 89.3% (150/168; 95% CI: 83.6%-93.5%) when the algorithm required two or more ICD-9-CM codes for a hepatic decompensation. However, an algorithm requiring only one ICD-9-CM code for (i) cirrhosis and (ii) a hepatic decompensation event, in the absence of a chronic liver disease code, yielded a PPV of 85.7% (30/35; 95% CI: 69.7%-95.2%). CONCLUSIONS: A coding algorithm that includes at least one ICD-9-CM code for cirrhosis plus one ICD-9-CM code for a hepatic decompensation event has a high PPV for identifying patients with ESLD. The inclusion of at least two codes indicative of a hepatic decompensation event increased the PPV. This algorithm can be used in future epidemiologic studies to examine the outcomes of a variety of long-term medical therapies in patients with ESLD. Copyright ? 2012 John Wiley & Sons, Ltd.     

Adverse events among nursing home residents with Alzheimer's disease and psychosis

PURPOSE: The objective of this study was to quantify rates of adverse events in a high-risk multi-morbid population of institutionalized patients with Alzheimer's disease (AD). METHODS: We conducted a retrospective cohort study among nursing home residents diagnosed with AD and psychosis during January 1998 to October 1999. Using the Medicare Minimum Data Set (MDS) and Medicare inpatient claims (ICD-9 codes), 7728 nursing home residents aged 55-95 years with AD and psychosis were identified for study. Potential adverse events of interest were identified from the MDS and Medicare inpatient claims (ICD-9 codes). We estimated the incidence rate (IR) and 95% confidence interval (CI) for each adverse event during a 2-year follow-up period. RESULTS: Of the 7728 residents studied, nearly 30% were considered 'dependent' by the activities of daily living (ADL) score and approximately 15% exhibited severe cognitive impairment at baseline. At least 90% had comorbid psychiatric disorders. The most common adverse event was accidental injury, occurring at a rate of 97.7 per 100 person-years (95%CI = 94.7-100.7). Other common adverse events were death (IR = 44.6/100 person-years; 95%CI = 42.9-46.4), infection (IR = 41.8/100 person-years; 95%CI = 39.7-43.8), pain (IR = 43.5/100 person-years; 95%CI = 41.2-45.9), anorexia (41.3/100 person-years; 95%CI = 39.1-43.6), and weight change (IR = 40.2/100 person-years; 95%CI = 38.7-41.7). CONCLUSIONS: This information on the occurrence of adverse outcomes among nursing home patients with AD and psychosis provides useful context for any safety event observed among patients treated for psychosis.     

Validation of ICD-9 codes with a high positive predictive value for incident strokes resulting in hospitalization using Medicaid health data

PURPOSE: To validate ICD 9 codes with a high positive predictive value (PPV) for incident strokes. The study population consisted of Tennessee Medicaid enrollees aged from 50 to 84 years. METHODS: We identified all patients who were hospitalized with a discharge diagnosis of stroke between 1999 and 2003 using highly specific codes (ischemic stroke ICD 9-CM codes 433.x1, 434 [excluding 434.x0], or 436; intracerebral hemorrhage [431]; and subarachnoid hemorrhage [430]). We reviewed medical records of a systematic sample of 250 cohort members. We randomly selected 10-30 eligible records for review from hospitals with at least 10 stroke hospitalizations. RESULTS: We reviewed 231 charts (93% of total sampled), and 205 (89%) met study criteria for new outpatient stroke. Of the 205 confirmed new outpatient strokes, 196 had stroke listed as the primary discharge diagnosis (PPV = 96%). However, 46 (23%) of the 196 patients identified by the primary diagnosis also had a remote stroke history (recurrent stroke not incident). Thus the PPV of the primary discharge diagnosis for identifying incident stroke decreased to 74%. When we applied an algorithm that restricted our population to those with stroke as the primary diagnosis and excluded patients with any prior outpatient diagnosis of stroke, we identified incident stroke events with more precision (PPV = 80%). CONCLUSION: The PPV of incident strokes was 80% using our strategy of primary discharge diagnosis and excluding prior outpatient diagnoses of stroke. Although an unknown percentage of incident strokes are missed, this group of proven incident stroke patients can be used for etiologic studies of medication exposures.     

Hospital admissions for 'drug-induced' disorders in England: a study using the Hospital Episodes Statistics (HES) database

AIMS: To review Hospital Episode Statistics (HES) data for England coded as being 'drug induced' during 1996-2000 and to consider their potential utility for assessing the public health burden of adverse drug reactions (ADRs) and studying drug safety. METHODS: ICD-10 codes including the words 'drug-induced' or 'due to' a medicine or which are recognized to be invariably caused by a drug were extracted along with external cause codes indicating that a drug was implicated (i.e. Y40-59 in ICD-10). We also calculated the proportions of patients with each 'drug-induced' code for whom an external cause code had been applied. RESULTS: During the 5-year study period there were almost 53.8 million hospital admissions in England, of which 44 411 (0.083%) were coded as 'drug-induced' and 168 958 (0.314%) were associated with a relevant external cause code. The numbers of patients with 'drug-induced' codes used were generally stable during the study period (range 7454-8860 per year) but the application of external cause codes increased in each year and by 40% overall (from 24 786 in 1996 to 34 843 in 2000). The overall proportion of 'drug-induced' codes associated with a relevant external cause code was quite low (12-15%) but there was considerable variation between codes. CONCLUSIONS: Comparisons with published studies indicate that HES data grossly underestimate the burden of drug-induced disorders as a cause of hospital admission. There are likely to be multiple underlying reasons including under-recognition, under-recording and limitations of the coding system. The potential of these data for identifying previously unrecognized serious ADRs is limited by constraints on the availability of detailed data regarding individual cases.     

Evaluation of the extent of under-reporting of serious adverse drug reactions: the case of toxic epidermal necrolysis.

INTRODUCTION: Toxic epidermal necrolysis (TEN) is a life-threatening adverse drug reaction (ADR) that is primarily the result of drug exposure (incidence 0.4-1.3 per million person-years). Life-threatening ADRs such as TEN should be reported to ADR monitoring programmes, which collect reports for suspected ADRs and alert the public and medical practitioners to new drug hazards. In Canada, reports are made to the Canadian Adverse Drug Reaction Monitoring Program (CADRMP). OBJECTIVE: To examine the extent of under-reporting for TEN in Canada. DESIGN: A retrospective case series design was used to collect all TEN cases for the period January 1995 to December 2000. METHODS: The CADRMP and 22 burn centres across Canada were contacted for all TEN patients treated during the specified time period. PATIENT GROUPS STUDIED: The study population consisted of patients admitted to burn treatment sites across Canada, patient cases reported to the CADRMP and patient cases recorded by the Canadian Institute for Health Information (CIHI) hospital discharge summaries as the International Classification of Diseases Version 9 Clinical Modification (ICD-9-CM) code 695.1. RESULTS: Twenty-five TEN cases (six fatal) were reported to CADRMP from January 1995 to December 2000. During this period, 14 (63.6%) burn treatment sites reported admission of 250 TEN cases. Hospital discharge summaries using the ICD-9-CM code 695.1 indicated that 4349 cases were admitted to hospital during this time period and it was estimated that 15.5% (n = 674) of these cases were TEN. Using the burn facility data as the denominator, 10% (25 of 250) of TEN cases were reported to CADRMP. Using CIHI data as a denominator, only 4% (25 of 674) of TEN cases were reported to CADRMP. CONCLUSIONS: There is serious under-reporting of TEN. Lack of reporting of life-threatening ADRs can compromise population safety. There is a need to increase awareness of ADR reporting programmes.     

Incidence of allergic reactions associated with antibacterial use in a large, managed care organisation.

BACKGROUND: Data on the incidence of serious allergic reactions to fluoroquinolone antibacterials are mainly derived from spontaneous reports that cannot be used to accurately estimate incidence. METHODS: This study estimated the drug-specific incidence of serious allergic reactions after fluoroquinolone, cephalosporin and phenoxymethylpenicillin potassium exposure, using claims for healthcare services with confirmation through medical record abstraction within a large health insurer database. Cohorts exposed to each antibacterial of interest (moxifloxacin, levofloxacin, ciprofloxacin, gatifloxacin, cephalosporins and penicillin) were identified, and followed for 14 days for anaphylaxis (9th revision of the International Classification of Diseases [ICD-9] code 995.0), other allergic drug reactions (ICD-9 995.2, 995.3) or cardiopulmonary resuscitation. RESULTS: The incidence per 10,000 first dispensings of any allergic diagnosis made in the hospital or emergency department was similar for moxifloxacin (4.3; 95% CI 3.5, 5.3), penicillin (4.7; 95% CI 3.8, 5.7) and ciprofloxacin (5.4; 95% CI 4.4, 6.5). The incidence for moxifloxacin was lower than that for levofloxacin (8.7; 95% CI 7.4, 10.0), gatifloxacin (6.7; 95% CI 5.6, 7.9) and the cephalosporins (7.5; 95% CI 6.3, 8.8). The incidence of anaphylaxis/anaphylactoid reactions after first dispensings was similar for the fluoroquinolones: 0.1 (95% CI 0.0, 0.3) for ciprofloxacin, 0.3 (95% CI 0.1, 0.5) for moxifloxacin, 0.3 (95% CI 0.1, 0.6) for gatifloxacin and 0.5 (95% CI 0.3, 0.9) for levofloxacin; and comparable with that of the cephalosporins (0.2; 95% CI 0.0, 0.4) and penicillin (0.1; 95% CI 0.0, 0.3). CONCLUSIONS: Anaphylactic reactions were rare and their incidence did not differ substantially among the drug groups studied. By determining the occurrence of reactions following defined exposures, these results provide a context for the interpretation of spontaneous reports of allergic reactions.     

Effect of neurotropin (NSP) on allergic reactions (author's transl)

A study was carried out to examine the effect on neurotropin (NSP) on the 4 types of allergic reactions classified by Coombs and Gell. 1) Type 1: NSP inhibited 48-hr homologous passive cutaneous anaphylaxis (PCA) as well as antigen-induced degranulation of rat mesenterium mast cells. The drug also inhibited both experimental asthma and histamine release from lung tissue in guinea pigs, as mediated by IgE antibody. 2) Type 2: NSP slightly suppressed the increase in urinary protein levels caused by nephrotoxic nephritis in rats and showed a tendency to inhibit Forssman shock in guinea pigs. NSP had an anticomplement activity in vitro but did not inhibit the reversed cutaneous anaphylaxis in rats. 3) Type 3: NSP suppressed an increase in the urinary protein level of rats with glomerulonephritis, as induced by immune complex. 4) Type 4: NSP slightly inhibited the increase in the urinary protein level in glomerulonephritic rats pretreated with IgG. However, the drug did not affect picryl chloride-induced contact dermatitis in mice. We conclude that NSP inhibits allergic reactions used in the present study except for reversed cutaneous anaphylaxis and contact dermatitis, and the most potent activity is seen in the case of Type 1 reaction.     

Administrative claims analysis of asthma-related health care utilization for patients who received inhaled corticosteroids with either montelukast or salmeterol as combination therapy

OBJECTIVE: To compare asthma-related health care resource utilization among a matched cohort of asthma patients using inhaled corticosteroids (ICSs) plus either montelukast (MON) or salmeterol (SAL) as combination therapy for asthma, during a time prior to the availability of fixed-dose combinations of ICS/SAL. METHODS: A retrospective analysis using the PHARMetrics patient-centric claims database was conducted for the period preceding the market introduction of combination fluticasone-SAL in September 2000. Patients had to meet the following criteria for inclusion in the study: they had to be between the ages of 4 and 55 years; they had to have been continuously enrolled for 2 years; they had to have initiated ICS/MON or ICS/SAL therapy between July 1, 1998, and June 30, 1999; and they had to have had either (a) a diagnosis of asthma (based on International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes of 493.xx) for 2 outpatient visits, 1 or more emergency department (ED) visits, or 1 or more hospitalizations within 1 year or (b) pharmacy claim records that contained a National Drug Code for an antiasthma medication (betaagonist, theophylline, ICS, cromolyn, or leukotriene) 2 or more times within 1 year. ICS/MON and ICS/SAL patients were matched 1 to 1 on age and propensity score. Outcomes included asthma-related hopitalizations and ED visits with ICD-9-CM codes of 493.xx, and oral corticosteroid (OCS) fills and short-acting beta-agonist (SABA) fills. Multivariate regression analyses were performed. Subgroup analyses based on sequential or concurrent initiation of combination therapy were also conducted. RESULTS: A total of 1,216 patients were matched (ICS/MON = 608; ICS/SAL= 608). Decreased odds of ED visits and/or hospitalizations were observed with ICS/MON (adjusted odds ratio [OR] = 0.58; 95% confidence interval [CI], 0.35- 0.98) versus ICS/SAL. The odds of postindex OCS fills were not different for ICS/MON and ICS/SAL patients (adjusted OR = 1.04; 95% CI, 0.79-1.38). Postindex pharmacy claims for SABAs were significantly higher among ICS/MON patients versus ICS/SAL patients (adjusted relative risk [RR] = 1.33; 95% CI, 1.17-1.52), and this difference remained regardless of prior use or no prior use of ICSs. In subgroup analyses, mean change in SABA fills varied by how combination therapy was initiated, with sequential addition of asthma controllers leading to a reduction in SABA fills in both groups. For patients with concurrent initiation of combination therapy, the odds of ED visits/hospitalizations were significantly lower in patients initiating ICS/MON (adjusted OR = 0.25; 95% CI, 0.08-0.79). CONCLUSION: In this matched cohort, use of ICS/MON compared with ICS/SAL resulted in similar odds of OCS fills, decreased odds of ED visits and asthmarelated hospitalizations, but higher utilization of SABA.     

Time courses of the anti-anaphylactic and anti-inflammatory effects of dexamethasone in the rat and mouse

1 The time course of the activity of dexamethasone has been studied in a variety of anaphylactic and inflammatory reactions in the rat and the mouse. 2 The times of peak activity of dexamethasone, expressed as time between oral dosage and induction of response, and the approximate ED50 values (mg/kg) found were: anaphylactic bronchoconstriction in rats, 12-24 h, ED50 1.8; passive cutaneous anaphylaxis in rats, 6 h, ED50 0.04; cutaneous reactions to histamine in rats, 4 h, ED50 0.01; carrageenin-induced paw oedema in rats, 4 h, ED50 0.03; pinnal anaphylaxis in mice, 6 h, ED50 0.82; histamine-induced pinnal reactions in mice, 6 h, ED50 0.05. 3 In rats, the characteristics of the inhibitory effects of dexamethasone indicate a differential activity against anaphylactic and inflammatory reactions and between different types of inflammatory reactions. Possible reasons for these differences are discussed. 4 In mice there was little difference between the inhibition by dexamethasone of cutaneous allergic and histamine-induced reactions. 5 Pinnal anaphylaxis in mice was potentiated by dexamethasone given 1-2 h before challenge.     

Validation of expert opinion in identifying comorbidities associated with atopic dermatitis/eczema

BACKGROUND: The use of expert opinion is widespread in economic studies of healthcare utilisation; however, few studies have attempted to assess the validity of assumptions derived from such sources. OBJECTIVE: To examine the use of such expert opinion in determining comorbidities associated with atopic dermatitis/eczema (AD/E), which were assessed as part of a recent third-party payer cost-of-illness study. DESIGN: To identify the disease-related comorbidities that would represent costs associated with AD/E, physicians on an expert panel were asked individually and then collectively to group all International Classification of Diseases, 9(th) Edition-Clinical Modification (ICD-9-CM) diagnosis codes as 'most likely', 'possibly' or 'definitely not' related to the costs of identifying and treating patients with AD/E. Claims representing $US464 million in payer reimbursements from nearly 125 000 patients with AD/E were identified within two separate claims databases (1997 values). Over 850 ICD-9-CM diagnosis codes were identified in the first-listed position from these claims. For each group of 'most likely', 'possibly' and 'definitely not' related diagnosis codes, prevalence rates were compared within AD/E and non-AD/E populations from the two historical payer claims databases. Adjusted and non-adjusted odds ratios were calculated by comparing prevalence rates between AD/E and non-AD/E patients in the same payer population. RESULTS: The mean prevalence rate of any diagnosis code in the AD/E population was 0.65 +/- 1.82% (SD) with a mean odds ratio of 1.81 +/- 0.96. Comorbidities considered by the expert panel 'most likely' to be associated with AD/E had higher prevalence rates (3.28 +/- 3.63%) and odds ratios (2.14 +/- 1.14). Comorbidities considered to be 'possibly' related to AD/E had prevalence rates and odds ratios of 3.01 +/- 5.06% and 1.84 +/- 0.82, respectively. Comorbidities considered to be 'definitely not' related to AD/E had the lowest prevalence rates (0.45 +/- 1.09%) and odds ratios (1.80 +/- 0.97). CONCLUSIONS: Comparing the result of consensus panels with actual claims histories validated the use of expert opinion in determining comorbidities associated with AD/E. Expert opinion yielded valid results in terms of identifying comorbidities that manifested frequently and disproportionately in the AD/E population. Limited statistical measurements of comorbidities would have been less specific than expert opinion. Future cost-of-illness studies should consider alternative data sources and methodologies to enhance the validity and importance of expert opinion and to corroborate their findings.     

Use of fluroquinolone and risk of Achilles tendon rupture: a population-based cohort study

Objective Several case-control studies have reported that the use of fluoroquinolone increases the risk of rupture of the Achilles tendon. Our aim was to estimate this risk by means of a population-based cohort approach. Setting Data on Achilles tendon ruptures and fluoroquinolone use were retrieved from three population-based databases that include information on residents of Funen County (population: 470,000) in primary and secondary care during the period 1991–1999. A study cohort of all 28,262 first-time users of fluoroquinolone and all incident cases of Achilles tendon ruptures were identified. Main outcome measures The incidence rate of Achilles tendon ruptures among users and non-users of fluoroquinolones and the standardised incidence rate ratio associating fluoroquinolon use with Achilles tendon rupture were the main outcome measures. Results Between 1991 and 2002 the incidence of Achilles tendon rupture increased from 22.1 to 32.6/100,000 person-years. Between 1991 and 1999 the incidence of fluoroquinolone users was 722/100,000 person-years, with no apparent trend over time. Within 90 days of their first use of fluoroquinolone, five individuals had a rupture of the Achilles tendon; the expected number was 1.6, yielding an age- and sex-standardised incidence ratio of 3.1 [(95% confidence interval (95%CI): 1.0–7.3). The 90-day cumulative incidence of Achilles tendon ruptures among fluoroquinolone users was 17.7/100,000 (95%CI: 5.7–41.3), which is an increase of 12.0/100,000 (95%CI: 0.0–35.6) compared to the background population. Conclusion Fluoroquinolone use triples the risk of Achilles tendon rupture, but the incidence among users is low. Grant support: there is no funding.     

Drug-related visits to a district hospital emergency room

The role of adverse drug reactions (ADRs) as a cause of hospital visits varies depending on the type of hospitals. Our aim was to determine the incidence of drug-related emergency department visits to a district hospital, and to identify the drugs and patient groups involved. All patient visits to the emergency department of a Finnish district hospital were evaluated prospectively for 6 months. The physician on duty and a clinical pharmacologist selected all possibly drug-related visits for further scrutinising. The causality assessment (drug-related or not) was judged according to WHO criteria, based on the patients' files, including laboratory and other data. Of the 7113 evaluated visits, 167 (2.3%) were "certainly" or "probably" drug-related; 102 (1.4% of all) were related to ADRs and 65 (0.9%) to intentional overdoses. The most common ADRs were gastrointestinal symptoms (n=17) caused by antibiotics, opioids, nonsteroidal antiinflammatory or cytostatic drugs. The International Classification of Disease (ICD-10) codes on patients' files were insensitive to disclose ADRs. The ADR patients were older (mean age 57 years) than the intentional overdose patients (38 years; P<0.001). Males predominated in the intentional overdose group (38 males, 27 females) but not in the ADR patients. The majority of intentional overdoses was caused by psychotropics. The ADRs lead to hospitalisation in a higher frequency (51%) than did the intentional overdoses (35%). In conclusion, the incidence of "certainly" or "probably" drug-related visits to the district hospital emergency room was relatively low. The ICH-10 codes on patients' files were found to be insensitive to disclose the ADRs, even when they lead to hospital admission, casting doubts on the usefulness of ICH codes alone in ADR evaluation.     

Anti-allergic effects of 1-(2-ethoxyethyl)-2-(4-methyl-1-homopiperazinyl)benzimidazole fumarate (KB-2413)

The effects of KB-2413 on four types of allergic reactions classified by Coombs and Gell were investigated. KB-2413 inhibited homologous passive cutaneous anaphylaxis and passive anaphylactic bronchoconstriction in guinea pigs mediated by IgE-like antibody, and ED50 values were 0.0017 mg/kg, p.o., and 0.022 mg/kg, p.o., respectively. KB-2413 also inhibited IgG-mediated anaphylactic bronchoconstriction in guinea pigs actively sensitized with egg albumin. Both complement-dependent immune hemolysis and complement-independent hypotonic hemolysis were inhibited by KB-2413 in a concentration-dependent manner. KB-2413 had no effect on the Forssman systemic reaction. The passive Arthus reaction in guinea pigs sensitized with anti-egg albumin rabbit serum was unaffected by KB-2413. However, the early stage of the active Arthus reaction in rabbits sensitized with egg albumin was inhibited. KB-2413 had an inhibitory effect on the efferent phase of delayed-type hypersensitivity induced by picryl chloride (PC-DTH) in mice. On the other hand, the afferent phase of PC-DTH in mice was unaffected. These results suggest that KB-2413 strongly suppresses type I allergic reactions, and it slightly suppresses type II, III and IV allergic reactions.     

Are People Who Inject Drugs Frequent Users of Emergency Department Services? A Cohort Study (2008–2013)

Background: Although people who inject drugs (PWID) have been described as frequent users of emergency services, the majority of research is cross-sectional and involves records from a single emergency department (ED). Objectives: We describe characteristics of state-wide ED presentations in a cohort of PWID, and compare presentation rates to the general population. We also examine characteristics associated with frequent ED use. Methods: We used data from a retrospective linkage of public ED presentations from a cohort of 678 PWID between January 2008 and June 2013. Common principal diagnoses were described using the International Classification of Diseases, Tenth Revision, Australian Modification (ICD-10-AM) chapter headings. The ED presentation trend was estimated using negative-binomial regression. Characteristics associated with frequent use of EDs were identified using generalized estimating equations (GEEs). Results: There were 3437 presentations over 4163.5 person-years (PY) and the most common principal diagnosis was injury, poisoning and other externalities (19%). ED presentations increased by 4% every six months (95% confidence interval (CI) 0.1%–0.8%) and were three times greater than the general population. A quarter (24%) of the cohort presented frequently, and they were more likely to have noninjury-related diagnoses and be aged below 30 years, and less likely to have nonurgent presentations and be male. Conclusions: PWID use EDs at a higher rate than the general population, and typically present with injuries and mental and behavioral disorders. Referrals to drug treatment, mental health, and social support services can improve patient care and reduce the burden on EDs.     

Validation of a claims-based diagnostic code for Stevens-Johnson syndrome in a commercially insured population

PURPOSE: To validate the administrative claims identification of a diagnosis of Stevens-Johnson syndrome (SJS) using medical records as the "gold standard" in a large, commercially insured US population. METHODS: Patients with >1 medical claim with the International Classification of Diseases, Ninth Revision, Clinical Modification code 695.1x between 1 July 2000 and 31 May 2007 were queried in the HealthCore Integrated Research Database(SM) , which contains administrative claims data for 14 commercial health insurance plans. Trained nurses and pharmacists abstracted pertinent information from the identified patients' medical records, which were then reviewed by two independent dermatologists to identify criteria to determine SJS diagnosis. Positive predictive values (PPVs) based on the claims and chart data were computed for all the cases. RESULTS: Medical charts for 200 claims-identified cases, with the International Classification of Diseases, Ninth Revision, Clinical Modification code 695.1x, were abstracted and reviewed by the dermatologists. A total of five cases (PPV?=?2.50%, 95%CI = 0.8%-5.7%) were determined to be SJS with clinical certainty. PPVs varied with data stratification: PPV for inpatient claims only (PPV?=?2.00%, 95%CI = 0.24%-7.04%), inpatient claims with 695.1x in first diagnosis field (PPV?=?4.11%, 95%CI?=?0.86%-11.54%), and final decisions of either clinical certainty or probable cases of SJS (PPV?=?6.00%, 95%CI?=?3.14%-10.25%). CONCLUSION: These findings demonstrate the difficulties associated with identifying rare disorders, which lack specific diagnostic criteria, within administrative claims databases. They underscore the challenges of using claims data to monitor ill-defined clinical conditions as well as the need to validate claims-identified cases with information from other sources, such as medical charts. Copyright ? 2012 John Wiley & Sons, Ltd.