| | The somatization in primary care study: a tale of three diagnosesAbstract Somatization is a common phenomenon that has been defined in many ways. The two most widely used diagnoses, Somatization Disorder (SD) and Abridged Somatization Disorder (ASD), are based on lifetime unexplained symptoms. However, reports indicate instability in lifetime symptom recall among somatizing patients. Multisomatoform disorder (MSD) is a new diagnosis based on current unexplained symptoms. To understand how knowledge about SD and ASD translates to MSD, we examined the diagnostic concordance, impairment and health care utilization of these groups in a sample from the Somatization in Primary Care Study. The diagnostic concordance was high between MSD and SD, but lower between MSD and ASD. All three groups reported considerable physical impairment (measured using the PCS subscale of the SF-36). The mental health (MCS) scores for the three groups were only slightly lower than those of the general population. Over the course of one year, physical functioning fell significantly for all three groups. Mental functioning did not change significantly for any of the three groups over this period. Utilization patterns were very similar for the three groups. The high prevalence, serious impairment, and worsening physical functioning over the course of one year suggest the importance of developing interventions in primary care to alleviate the impaired physical functioning and reduce utilization in somatizing patients. MSD should be a useful diagnosis for targeting these interventions because it identifies a sizable cohort of somatizing patients reporting impairment of comparable severity to full SD, using a more efficient diagnostic algorithm based on current symptoms.
1. Introduction  Somatization has been defined in multiple ways, [1], [2], [3], [4], [5], [6], [7], [8], [9] but generally is understood to mean the occurrence of clinically significant physical symptoms that cannot be entirely explained by physical disease. Somatization occurs frequently in primary care, where up to half of all primary care visits are for somatic complaints and one-third remain unexplained. [10], [11], [12], [13], [14] The diagnosis of somatization disorder (SD) evolved out of the earlier concepts of neurasthenia, hysteria and Briquet’s syndrome. SD was first defined in the DSM-III, based on a lifetime history of unexplained symptoms. [15] The DSM-IIIR modified the criteria to require 13 of a list of 35 lifetime unexplained physical symptoms. [16] The DSM-IV defined a complex algorithm requiring unexplained symptoms from several different categories. [3] Reported prevalence of SD ranges from 0.1% to 16% in various populations, typically about 1–5% in primary care patients. [13], [17], [18] Because many patients who somatize do not meet criteria for full somatization disorder, Escobar proposed and validated a less severe form of somatization called abridged somatization disorder (ASD). [4], [19] ASD is also based on patient recall of lifetime symptoms, requiring at least six unexplained symptoms in women and four in men. Studies report prevalence of ASD ranging from 8 to 37%. [4], [6], [13], [17] The diagnoses of SD and ASD are made on the basis of lifetime unexplained symptoms. However, the WHO Study of Psychological Problems in Primary Care suggested that recall of lifetime somatic symptoms among somatizing patients is unstable. [20] Although another study indicated that the overall tendency of patients to somatize is a more stable phenomenon, [21] these reports have cast some doubt on the reliability of diagnoses based on recall of lifetime somatic symptoms. Recent investigators have explored the validity of multisomatoform disorder (MSD), which is based on current unexplained symptoms [22], [23]. MSD requires the presence of three or more unexplained symptoms within the past two weeks out of a list of 15, along with a two-year history of somatization. Reported prevalence of MSD in primary care ranges from 4% to 18% [22], [23]. To better understand how the newer diagnosis based on current symptoms relates to older diagnoses based on lifetime symptoms, we examined the diagnostic concordance, impairment, and health care utilization of subjects with SD, ASD, and MSD using data from the Somatization in Primary Care Study, a longitudinal investigation of somatization treatment in a representative population of primary care patients. 2. Materials and methods 2.1. Study design The Somatization in Primary Care Study is a five-year NIMH-funded study conducted in three family practices in or near Mobile, Alabama, USA. Practice sites were selected to achieve geographic and socioeconomic diversity, with one urban practice that serves a racially and economically diverse population, and one suburban practice and one rural practice that both serve higher socioeconomic populations. The results reported are part of a large randomized controlled trial evaluating the impact of a care recommendation letter for somatization. All subjects who were originally classified as meeting criteria for full somatization disorder or subthreshold somatization (defined as 6–12 lifetime symptoms) were randomized to one of two arms of a randomized single crossover trial. The primary care physician was notified by letter of the patient’s somatization status either immediately following baseline for approximately half the subjects or one year after enrollment for the remainder of the subjects. The letter also included guidelines for management of somatization by primary care physicians. [24] This paper reports results from the enrollment assessment for all subjects by somatization diagnoses. We also report results from six and twelve-month follow-up assessments for subjects who received the letter intervention twelve months after enrollment, because these subjects provide an opportunity to observe the natural history of somatization over a year with usual care. Results of the intervention trial will be reported elsewhere. 2.2. Training of interviewers Female interviewers were trained by an external consultant and by members of the research team (WPD, LMD, FdG) in interviewing and data collection procedures, including administration of the Diagnostic Interview Schedule (DIS) [25] and a structured genogram assessment. [26] Screening and enrollment procedures were manualized. 2.3. Screening and sample selection The screening window covered thirteen months beginning in February 1992. In each practice, an interviewer screened patients in full-day blocks distributed evenly throughout the week. Concurrent patients who presented for care for any reason during the screening days were asked before the visit to complete an eleven-item screen [27], [28] for unexplained physical symptoms, consisting of a subset of the 37 symptoms from the DSM-III-R criteria for Somatization Disorder [16]. All patients with three or more positive items on the screen were invited to enroll in the study, along with a sample of consecutive patients with fewer than three symptoms not meeting criteria for full or subthreshold somatization, who were frequency matched to the age/race/gender distribution of the combined somatization groups. Written informed consent was secured in accordance with the protocol approved by the Institutional Review Board at the University of South Alabama College of Medicine. Subjects who agreed to participate were scheduled for a face-to-face enrollment interview either in the physician’s office or in their own homes within 14 days after the index visit. Each enrollee completed the somatization section of the NIMH Diagnostic Interview Schedule (DIS) Version III-R [25] administered by one of four trained female interviewers. All DIS somatoform symptom results were subjected to physician review (FdG or WPD) prior to final coding to confirm that physical symptoms reported by the patient were medically unexplained. On the basis of the results of the DIS interview, enrollment proceeded until there were sufficient subjects to fill three approximately equal-sized groups: somatization disorder with 13 or more lifetime unexplained physical symptoms from the somatization section of the DIS, subthreshold somatization with 6 to 12 lifetime unexplained symptoms, and controls with fewer than 6 lifetime unexplained physical symptoms. The sample size was predetermined by power analysis to be adequate to find .25 effect size differences between SD and subthreshold somatization across a range of outcomes with 80% or greater power. Screening data available for virtually all adult patients presenting for care during the screening blocks was used to construct weights for prevalence estimates generalizable to the patient population in the three practices. 2.4. Reclassification of subjects During the course of this study two factors encouraged the research team to reclassify subjects using alternative diagnostic criteria. First, as mentioned previously, the reports of instability in lifetime somatoform symptom recall cast some doubt on the reliability of diagnoses based on lifetime somatic symptoms. [20] Second, the PRIME-MD studies preliminarily validated MSD as a new classification for somatizing patients based on the presence of current unexplained symptoms along with a history of somatization. [23] The enrollment interview data were reclassified to categorize each subject as meeting criteria for somatization disorder (SD), abridged somatization disorder (ASD), multisomatoform disorder (MSD), or no somatization diagnosis, allowing subjects to meet criteria for one or more of the somatization diagnoses. Standard probes from the somatic symptom section of the DIS were used to determine recency and duration of symptoms to meet MSD criteria for 3 current symptoms with a 2-year history of any of the eligible somatization symptoms. Design weights, based on the ratio of the total number of subjects within a screening stratum to the number selected for the study, were constructed so that the weighted prevalence of each diagnosis in the analytic sample approximated its expected prevalence in a consecutive sample of primary care patients. 2.5. Baseline and follow-up assessment Sociodemographic covariates were collected at baseline and included age, gender, race, education (highest grade completed) and Hollingshead social class, scored from 1 (low) to 5 (high) [29]. Co-morbid psychiatric diagnoses were made using the DIS (DSM-III-R version) and included major depression, dysthymia, panic disorder, substance disorder, or PTSD within the past 12 months [16]. Chronic physical disease was assessed at enrollment by the Medical Outcomes Study checklist [30] and reviews of the subjects’ medical records, with a positive finding defined by either patient report or record review. Chronic physical problems assessed included hypertension, diabetes, cardiac disease and pulmonary problems (asthma, chronic bronchitis, or emphysema). Functional impairment was evaluated using the MCS and PCS subscales of the Medical Outcomes Study SF-36 [31]. Both subscales have population norms of 50, with lower scores representing worse functioning. Follow-up assessments of functional impairment were carried out by telephone interview at 6 and 12 months post-enrollment, with follow-up rates of 94.0% and 86.8%, respectively. Risk factors were measured using a structured genogram interview to elicit family and personal history [26] and a previously validated abuse questionnaire [32], [33]. Health care utilization was assessed for one year prior to enrollment in the study by reviewing medical records from all healthcare providers seen during that time [34]. Utilization categories consisted of primary care visits, medical specialty care visits, mental health specialty visits, emergency room visits and hospitalizations. 2.6. Statistical analysis Statistical analysis was performed using SAS, Version 8 [35] and SPSS, Version 9.0 for personal computer [36]. Prevalence estimates were obtained by the method of direct adjustment using screen scores to approximate the sampled population distribution [37]. Due to diagnostic overlap among the three somatization groups, separate analyses were performed comparing MSD, ASD and SD to controls to determine how functional impairment and healthcare utilization varied across the three diagnoses. Longitudinal analyses were carried out using general linear mixed models (time trend or repeated measures) for subjects randomized to the group receiving the intervention at one year after enrollment [38]. The 92 subjects who were negative for all three somatization diagnoses constituted the control group. When analyses adjusting and not adjusting for sociodemographic and clinical covariates produced comparable findings, we elected to present nonadjusted analyses to facilitate comparisons with population norms (adjusted analyses available from authors on request). Patterns of missing data were examined for possible bias due to dropout, and a sensitivity analysis was carried out to investigate the possibility of nonignorable missingness. There was no evidence of the latter. Use of multiple imputation and pattern mixture models yielded similar results in all analyses. Therefore, reports of longitudinal analyses based on all available data are included here. Subject weights, described previously, were used in all analyses. 3. Results A total of 2,902 primary care patients were screened. Fourteen percent of the patients screened were unavailable for enrollment, 6.7% due to refusal and the remainder due to inability to contact or other difficulties. In the enrollment sample of 280 subjects, the estimated prevalence of ASD was 23.0%, MSD was 19.0%, and SD was 5.4%. 3.1. Sociodemographic and clinical characteristics The description of the sociodemographic and clinical characteristics of participating subjects may be found in Table 1. The amount of comorbid psychiatric and chronic physical disease across all three somatization groups is striking, with almost two-thirds of the MSD group having a comorbid chronic physical condition and almost half having a comorbid psychiatric condition over the previous year. 3.2. Diagnostic concordance Altogether, 95.5% of subjects who met criteria for MSD also met criteria for either ASD or SD. Of the 88 subjects who met criteria for SD, 83% also met criteria for MSD. Among subjects who met criteria for ASD, 47% also met criteria for MSD. 3.3. Impairment As Table 2 shows, PCS and MCS scores across all somatization diagnoses are statistically comparable. All three somatization groups reported considerable physical impairment, reflected by PCS scores that are significantly lower than the general population norm of 50. Although mean MCS scores for all three groups are slightly lower than the population norm of 50, this was statistically significant only in the MSD group. | | |  | SF-36 Summary scores | Control (N = 92) | ASD (N = 183) | MSD (N = 111) | SD (N = 88) | |
|---|
| Mean PCS (95% CI) | 48.0 (45.8, 50.2) | 43.4 (41.6, 45.2) | 41.8 (39.5, 44.1) | 41.2 (38.6, 43.8) | |
| Mean MCS (95% CI) | 51.8 (50.1, 53.5) | 48.7 (47.4, 50.0) | 47.7 (45.9, 49.5) | 48.1 (46.1, 50.1) | | | | |
3.4. Longitudinal impairment PCS and MCS scores were examined during the year after enrollment using random effects growth curve models (random intercept, random slope), adjusting for sociodemographic and clinical covariates. In subjects receiving usual care, PCS scores fell significantly for all three somatization groups, with an average one-year decline of 5.2 points for ASD (t = −2.85, P = .0046), 5.4 points for MSD (t = −2.37, P = .0185), and 7.3 points for SD (t = −2.66, P = .0084). The MCS scores did not change significantly for any of the three groups over this period. 4. Discussion The Somatization in Primary Care study provides important insights about the overlap among three commonly used somatization diagnoses: full (lifetime) somatization disorder, abridged (lifetime) somatization and (current) multisomatoform disorder. This study demonstrates that the majority of patients who meet diagnostic criteria for MSD also meet criteria for ASD or SD, although the extent of MSD overlap with SD is higher than with ASD. Thus, knowledge of somatization and its treatment derived from studies of SD and, to some extent, ASD patients may generalize to MSD patients given the considerable diagnostic overlap. Comparing functional status across the three diagnoses demonstrates more similarities than differences. MSD appears to have an impact on quality of life generally intermediate to that seen with SD and ASD. What is more striking about these scores is that somatizers, independent of their specific diagnosis, report physical functioning close to 1 SD below national norms, while reporting emotional functioning that reflects only mild levels of impairment. While these patterns may be somewhat biased by the forced independence between the two subscales, [39] our examination of the eight SF-36 subscales demonstrates a similar pattern, with the mental health (MH) subscale only slightly lower than national norms (available from authors on request). This pattern is somewhat surprising given the extensive psychiatric comorbidity in referred samples. Somatizing subjects with current mental health diagnoses report lower MCS scores than somatizing subjects as a group (available from authors on request). For most somatizing patients the higher than expected MCS scores may reflect the extent to which these patients see themselves as physically and not emotionally ill. Somatizers in this sample appear to have more chronic physical disease than nonsomatizers, possibly reflecting the increased opportunities somatizers have to receive diagnoses during multiple visits and tests. Also patients diagnosed with chronic physical disease probably monitor physical symptoms more closely than patients without chronic disease and thus are more likely to notice symptoms that may or may not have a physical explanation. The increase in physical deterioration over one year in all three groups is both impressive and surprising, providing important information for the design and evaluation of primary care interventions to improve somatization outcomes. Interventions that maintain such patients at baseline levels of physical functioning after a year could be judged successful given the substantial decrements with usual care. Comparing health care utilization patterns across the three diagnostic groups also demonstrates more similarities than differences. Other studies have demonstrated the considerable increase in utilization associated with SD and ASD compared with control populations. [40], [41], [42], [43], [44], [45] These results demonstrate that MSD is associated with a level of increased utilization that is comparable to that of the other somatization diagnoses, suggesting that it may be possible to achieve cost offsets in MSD with interventions that produce cost offsets in SD [24], [46] and subthreshold somatization. [47] To our knowledge there have been only three other studies of somatizing patients in the U.S. that have drawn samples from consecutive samples of primary care patients: the WHO Study of Psychological Problems in General Health Care which assessed full and abridged (lifetime) somatization, [17] Escobar’s study of primary care patients with abridged somatization, [6] and the PRIME-MD study of multisomatoform disorder. [23], [48] Studies that identify subjects by screening a general primary care population without depending on provider identification probably capture a more heterogeneous group of somatizers who could be potentially reached with systematic screening and intervention. A major strength of the Somatization in Primary Care study lies in the recruitment of a consecutive sample of primary care patients with both sociodemographic and ethnic diversity. Our study includes a broader assessment of comorbidity, both psychiatric and medical, than previous studies of MSD have been able to include. In addition, we have collected more extensive measures of healthcare utilization than are available from existing studies, which shed important light on MSD patients’ help-seeking patterns. Perhaps most importantly, longitudinal assessment of impairment provides essential information for designing an intervention to improve, or at least stabilize, declining functional impairment in somatizing patients. This study is also limited in several ways. First, the data comparing the three somatization diagnoses were derived from original study groups that were based on a continuum of unexplained symptoms. While the reclassified groups overlap considerably, the weighting techniques we employed should produce results comparable to studies recruiting nonoverlapping groups. The original study validating MSD derived the diagnosis from a list of fifteen symptoms that patients reported as unexplained. We used the DIS and physician review to ascertain that physicians agreed these symptoms were unexplained. [23], [25] Subsequent exploration indicated that these two approaches produce substantial diagnostic concordance (results available from authors). Even though we screened 860 men for eligibility into this study, state of the art screening captured only 11 male somatizers. The decreased sensitivity associated with setting the threshold on the screener at three or more symptoms left many SD and ASD men in the negative screen group, comingled with a large pool of relatively asymptomatic men. Few of these somatizing men were subsequently captured by our random selection from this large pool and so relatively few men received the full DIS interview. Thus, our screening methodology was not efficient for men. This resulted in a small but representative sample of men available for analysis. This is a relatively large sample of primary care patients drawn from three diverse practice settings, but they are confined to one geographic region of the United States. Major cultural differences in somatization have been demonstrated internationally, [17], [49] and regional differences within large countries may also exist. [50] Likewise, although the three practices were chosen to represent distinctly different primary care practices, our utilization results may not be generalizable to all primary care practices across the country, particularly those that treat primarily capitated populations. The findings from this study suggest that MSD provides an efficient diagnostic method for identifying primary care somatizers who need treatment. MSD identifies a sizable cohort of somatizing patients reporting impairment of comparable severity to full somatization disorder without the limitations associated with recall of lifetime symptoms. MSD may be also easier to assess than ASD or SD, being based on a list of 15 current rather than 35 lifetime symptoms. The high prevalence, serious impairment, and deterioration over the course of one year suggest the importance of developing primary care interventions to alleviate the physical burden that somatizers suffer. 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Psychosomatics. 1989;30(1):44–53. MEDLINE a Department of Family Medicine, University of Colorado Health Sciences Center, Denver, CO, USA b Department of Family Medicine and Community Health, University of Massachusetts Medical School, Worcester, MA, USA c Department of Psychiatry, University of Colorado Health Sciences Center, Denver, CO, USA  Corresponding author. Tel.: +1-303-724-9754; fax:+1-303-724-9747.
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