Wednesday, February 01, 2017

Screening for Diabetes...does it make sense?

In order for a disease to be a candidate for screening it has to satisfy the following seven criteria1: 

  1. it has to be an important health problem 
  1. the natural history of the disease is well known 
  1. it has to have a recognizable preclinical asymptomatic stage 
  1. tests that can detect the preclinical stage are available 
  1. offering treatment after early detection is of proven benefit 
  1. the process has to be cost effective 
  1. screening has to be an ongoing process 

Diabetes Mellitus can be broadly classified into type 1, type 2, and diabetes due to other causes (including gestational diabetes). Whereas  screening for diabetes type 1 is not advised because there is no treatment recommendable for the asymtomatic phase2, diabetes type 2 meets conditions 1 to 4 (conditions 5 to 7 are not met entirely)1. Furthermore diabetes type 2 accounts for 95% of diabetes patients in the United States and its global prevalence is increasing2. 

Nonetheless there are differing expert opinions on whether to screen for diabetes. For example the UK National Screening Committee recommends against screening for diabetes type 23. On the other hand in the United States and Canada screening is recommended for patients at risk of diabetes type 2 or its complications2. 

Screening for diabetes type 2 may take the form of a questionnaire, formal laboratory investigations or a combination of the two4.  Fasting plasma glucose (FPG) is the preferred test1 for the following reasons: 

  1. easier to perform1 
  1. faster to perform1 
  1. patients find it more convenient and acceptable1 
  1. relatively inexpensive1 
  1. has relatively high sensitivity and specificity4 

The screening programme may take one of the following approaches4 

  1. target an entire population 
  1. target only those at risk of a disease 
  1. screen opportunistically 
  1. screen haphazardly 

Opportunistic screening is testing done for a particular disease or condition during patient encounters for unrelated problems. Haphazard screening is done on subjects chosen at random, for example testing customers at a supermarket. 

In the maltese context screening for diabetes type 2 occurs to a greater or lesser extent at primary care level5. The type of screening is opportunistic. Patients either request routine blood investigations (including, but not limited to FPG), or these are offered by the physician during a consultation for another reason. Patients testing positive are then offered one or a combination of the following: 

  1. lifestyle and dietary advice 
  1. pharmacological treatment 
  1. referral to secondary care 

My suggestion is, in line with WHO recommendations4, to adopt the following improvements to the screening already being done in Malta: 

  1. formulation of a clear policy on screening including all the stakeholders which should be reviewed periodically as new evidence materializes 
  1. carrying out randomized controlled trials(RCT) on the efficacy of screening, or if this is not feasible logistically and economically, participating in any which may be currently running 
  1. carrying out a feasibility study comparing early detection versus other preventive and therapeutic options 
  1. haphazard screening should be discouraged 
  1. those being screened should be given an explanation as to why they are being tested 
  1. testing should be done with investigations of adequate sensitivity and specificity 
  1. addressing the psycho-social needs of those testing positive and negative 
  1. the screening should take into consideration the epidemiology of diabetes type 2 and related cardiovascular complications 
  1. screening should take into account competing health priorities 
  1. the screening being carried out should be formally evaluated


References 
  1. Diabetes Care January 2002 vol. 25 no. suppl 1 s21-s24  
  1. Am Fam Physician. 2010 Apr 1;81(7):863-870.    
  1. http://www.who.int/diabetes/publications/en/screening_mnc03.pdf  
  1. Personal professional experience in Primary Health Care