BEYOND SEQUENCING FOR MEDICAL PRACTICE PATTERN ANALYSIS: THE USE OF HIERARCHICAL CLUSTER ANALYSIS WITH AN APPLICATION TO URETEROLITHIASIS

Purpose: Sequencing analysis has traditionally been used to describe medical practice patterns.  Unfortunately, sequencing can result in many patterns accounting for a small proportion of variance with overly simplistic interpretations. Hierarchical Cluster Analysis (HCA) provides an alternative method that summarizes characteristics into a few prototypic patterns. This study illustrates the superiority of HCA over sequencing in describing ureterolithiasis treatment patterns.    

Method: A random sample of 5000 ureterolithiasis patients was identified from administrative claims between 2008 through 2011.  Diagnostic imaging and treatment interventions were extracted and analyzed in sequence analysis and then HCA.  Obtained patterns were compared on service site, practitioner specialty, costs, imaging, and interventions.

Result:

Sequencing generated 167 patterns accounting for all patients and 25 sequences accounted for 90% of cases.  The first three sequences (60%) were associated with CT scanning, pain medication in two, and medical expulsion therapy (MET) in one.  Further analyses showed the first two sequences were associated with emergency department (ED) treatment (85%), while pattern 3 yielded no clear distinctions.  No cost or other differences were observed.

   Conversely, HCA retained 100% of patients in three interpretably meaningful practice patterns: watchful waiting (WW), complex-invasive treatment (CI), and urgent care (UC).  The WW pattern was associated with outpatient treatment (45%) by primary care physicians (50%).  The CI pattern was associated with both outpatient and inpatient service sites (46%) and Urologists (56%).  The UC pattern was associated with ED (85%) and ER physicians (60%).  WW showed the lowest frequency of CT imaging (65.6% versus CI (78.7%) and UC (99.8%)) (P < 0.001), the lowest use of MET (15.0% versus CI (23.1%) and UC (36.9%)) (P < 0.001).  On average, CI cost $1,580 more per patient than WW and $1,359 more than UC (P < 0.05).  UC cost $508 more per patient than WW (P < 0.05).  CI was associated with higher use of ureteroscopy and shock wave lithotripsy treatments (P < 0.001).

Conclusion: HCA obtained three distinct practice patterns accounting for 100% of ureterolithiasis cases compared to sequencing, which required 167 distinct patterns to account for all patients.  Furthermore, HCA provided interpretable and meaningful practice patterns; whereas, the patterns obtained from sequencing did not correspond with other external variables.  Research aimed at describing practice patterns should consider HCA as an alternative to sequencing when appropriate.