Relating Subjective and Objective Pharmacovigilance Association Measures - Clustering Challenges in Biological Network - page 296

15.7. Interpreting the Clusters

Examination of the drug classifications in the clustering results described in Sec.
15.6.3 shows that the partitions are all quite similar. Consequently, the following
discussion first presents a detailed description of the basic clustering obtained for
k ∗ =3from the three variables V 1 , V 2 ,and V 3 , and then briefly discusses how
the results obtained from the other variable subsets differ from this reference case.
The first cluster in the basic clustering contains the following 21 drugs:

accupril, aminocaproic acid, aspirin, atenolol, azesetron, bactrim,

candesartan, ciprofloxacin, clonadine, clopidrogel, dipiperon, hy-

drochlorothiazide, insulin, levodopa, lorazepam, metroprolol, mi-

anserin, omeprazole, oxaprozin, prednisone, and zolpidem.

The general characteristics of this cluster are a low mean S ab value (the me-
dian V 1 value is 0 . 161), and low correlations between S ab and both R ab (me-
dian correlation 0 . 048)and U ab (median correlation 0 . 131). Informally, this clus-
ter represents a collection of drugs that tend to have “low subjective suspicion,”
largely independent of objective evidence. The second partition in the basic clus-
tering contains the following 13 drugs:

aldioxa, atorvastatin, coumadin, depamide, fluoxetine, ibuprofen, lo-
vastatin, morphine, oxycodone, paracetamol, pravastatin, simvastatin,
and tamsulosin.

The defining characteristics of this cluster are moderate mean S ab values (the
median V 1 value is 0 . 301) and substantial correlations between S ab and both R ab
(median correlation 0 . 426)and U ab (median correlation 0 . 525). Informally, this
cluster represents a collection of drugs whose subjective suspicion level seems to
correlate reasonably well with objective evidence. Finally, the third partition in
the basic clustering contains the 17 drugs:

bosentan, carbamazepine, cisplatin, clozapine, cocaine, dutasteride,
etanercept, galantamine, gatifloxacin, infliximab, levofloxacin, lupro-
lide, moxifloxacin, mycophenolate, rofecoxib, tenofovir, and valde-
coxib.

This cluster is characterized by a large mean S ab value (the median V 1 value is
0 . 678), a moderate correlation between S ab and R ab (median correlation 0 . 353),
and a low correlation between S ab and U ab (median correlation 0 . 079). Infor-
mally, the drugs in this cluster exhibit high subjective suspicion, largely indepen-
dent of objective evidence.