How to Choose a Reliable Medical Laboratory in the Arab World

Why can two labs give different results on the same sample?

If you repeat a test at a different laboratory and get a different number, this is more common than you might expect. It does not always mean that one lab made a mistake. Every lab uses different instruments, different reagents, different calibration standards, and these differences can produce genuinely different results even from the same sample.

This is not a criticism of laboratories but a documented physical and chemical reality. A landmark paper in Clinical Chemistry and Laboratory Medicine by Professor Mario Plebani in 2006 showed that most laboratory errors occur before and after the analytical measurement, and that systematic differences in method between labs account for much of the result variation that patients notice. The quality systems described in this article exist precisely to minimise that variation.

A small difference between two well-run labs is scientifically acceptable and does not usually affect a clinical decision. A large difference is a warning that one or both labs may have a problem with instrument drift or calibration, and your doctor can advise you whether to repeat the test or which result to trust.

What is laboratory accreditation and why does it matter to you?

Laboratory accreditation is a certificate awarded by an independent assessment body confirming that a lab meets documented standards of quality and safety. The two most internationally recognised standards are ISO 15189, the global quality standard for medical laboratories, and the CAP programme run by the College of American Pathologists, which is common in Gulf, Egyptian and Jordanian laboratories.

Accreditation under ISO 15189 means the lab has undergone periodic review by external assessors who verified staff competence, instrument accuracy, working procedures, emergency protocols and how samples are handled from the moment they arrive. The 2025 IFCC recommendations on ISO 15189:2022 implementation confirm that accredited labs operate within a structured daily internal quality control framework that non-accredited labs are not required to maintain.

The absence of accreditation does not automatically make a lab bad. Many excellent labs have not applied for accreditation for administrative or cost reasons. But accreditation means a lab has proved its quality to an independent party rather than only to itself. In the Arab world context, where regulatory oversight varies considerably from country to country, accreditation is the most objective standard an ordinary patient can check.

What is internal quality control and how does it protect you?

Internal quality control is a system in which the lab runs samples of known concentration every day to confirm that its instruments are producing correct results. If the control result falls outside the acceptable range on a given day, a properly run lab must stop patient testing until the problem is identified and corrected. This is not optional in an accredited lab: it is a daily discipline.

In labs that do not run regular internal quality control, instruments can drift over time, producing systematically high or low results without anyone noticing. This gradual bias is exactly what quality control systems are designed to detect before a patient is affected by it. The 2023 paper on quality indicators in laboratory medicine published in Clinical Chemistry and Laboratory Medicine describes how consistent internal QC data is the foundation of any reliable result, and how labs that track quality indicators longitudinally maintain tighter control over analytical performance.

As a patient you cannot inspect a lab's quality control records, but you can ask a direct question: do you run internal quality control every day? ISO 15189 accreditation obliges labs to do so, which is why asking about accreditation is in practice asking about quality control. A lab manager or senior technician in a well-run lab should be able to explain their QC approach in plain terms without difficulty, because it is part of their daily routine.

What is external quality assessment and why does it matter?

External quality assessment, sometimes called proficiency testing, is a system in which an independent organisation sends a lab unknown samples and then compares that lab's results against hundreds of other labs that received the same samples. The comparison tells the lab exactly where its performance sits relative to a peer group.

A 2011 paper in Clinical Chemistry by Miller and colleagues showed that external quality assessment is the most powerful available tool for detecting systematic bias in laboratory performance, and that labs that participate regularly in structured programmes show consistently higher accuracy over time. A 2025 study confirmed that pre-analytical phase errors now account for the majority of remaining errors in labs that have controlled their analytical phase through robust EQA participation.

The best-known international programmes are UK NEQAS, the Scandinavian RIQAS scheme and the CAP proficiency testing programme. In the Arab world, large hospital labs in the Gulf, Jordan and Egypt often subscribe to one of these. Asking the lab which external programme it belongs to is a reasonable question that a well-organised lab will be able to answer immediately.

The questions to ask at reception

You do not need a scientific background to evaluate a laboratory. A few direct questions at reception reveal a great deal. Ask: is this laboratory accredited to ISO 15189 or CAP? Do you participate in an external quality assessment programme? Do you perform all tests in-house or do you send some to a reference laboratory? How long does the result take and is it available electronically? Who can explain an unexpected result to my doctor?

A well-managed reception desk will know the answer to the accreditation question, or will direct you to the laboratory director. If the question is met with silence or genuine unfamiliarity, that too is informative. Labs that invest in quality tend to talk about it naturally as part of how they describe their service.

The question about reference laboratories is also worth asking. Sending specialised tests to a larger reference lab is entirely normal and often preferable to running them on ageing equipment in-house. What matters is that the lab is honest about which tests it runs locally and which it refers, and that the reference lab it uses is itself of high quality.

Why location and appearance are not enough

A central location, a modern fitout and a large network of branches do not guarantee the quality of results. Some of the most widely distributed laboratory chains in Arab cities have no external accreditation and do not subscribe to any external quality assessment programme. Conversely, a smaller lab in a less central area may hold ISO 15189 accreditation and deliver more accurate results.

Price is equally unreliable as a quality indicator. Accredited labs may charge slightly more because of the cost of maintenance, proficiency programmes and periodic audits, but the most expensive option is not always the most accurate. Look for accreditation and external quality participation regardless of price.

Proximity matters for practical reasons, especially for early-morning fasting tests or for elderly patients. But for tests where accuracy is critical, such as a cancer marker, a genetic panel or the monitoring of a serious chronic disease, a slightly longer journey to a better-equipped lab is a genuine investment in the reliability of your diagnosis.

Matching the lab to the type of test

Not every test requires a large accredited lab. A full blood count, fasting glucose, cholesterol, liver and kidney function: these are routine tests that any well-organised general lab can perform reliably. The need for a specialist lab becomes more urgent when the test has a narrow acceptable error margin and the result will directly drive a treatment decision.

Hormone panels including FSH, LH, progesterone, testosterone and AMH; genetic and chromosomal testing; semen analysis; cancer markers such as PSA, CA-125 and CEA; and all molecular diagnostic tests: these call for a specialist lab and ideally one with accreditation specific to that type of testing. The analytical equipment, the calibration standards and the staff training required for these tests are quite different from those needed for routine biochemistry.

In Saudi Arabia, the UAE, Jordan and Egypt, national accreditation bodies publish lists of accredited laboratories that are publicly accessible. If you cannot find this information easily online, ask your treating doctor which lab they use for their own patients' tests. A doctor who reads lab results daily builds up reliable empirical knowledge of which labs in their area are trustworthy.

How to get more from your results, whatever the lab

However good the laboratory, a single result does not constitute a diagnosis. The function of a test result is to add a piece of information to a broader picture that your doctor builds from your medical history, physical examination and symptoms. A result outside the reference range does not necessarily mean disease, and a result within the range does not guarantee that everything is fine.

A very common pattern in the Arab world is for patients to order multiple tests without a referral and then try to interpret the results themselves using internet searches. This leads either to unnecessary anxiety about a variation that is clinically unimportant, or to false reassurance about a pattern that does need attention. The lab provides accurate data; interpreting it correctly requires a doctor who knows your full context.

Always keep a copy of your results, noting the name of the lab and the date. This allows your doctor to compare results over time and to notice trends, which is often far more valuable than a single isolated measurement. A value that has changed by 20 percent over six months is more informative than whether it falls inside or outside a normal range on one occasion.

Sources

• Giannoli JM, Vassault A, Carobene A et al: Ensuring internal quality control practices in medical Laboratories: IFCC recommendations for practical applications based on ISO 15189:2022, Clinica chimica acta, 2025
• Plebani M: Errors in clinical laboratories or errors in laboratory medicine?, Clinical chemistry and laboratory medicine, 2006
• Lin Y, Spies NC, Zohner K et al: Pre-analytical phase errors constitute the vast majority of errors in clinical laboratory testing, Clinical chemistry and laboratory medicine, 2025
• Sciacovelli L, Padoan A, Aita A et al: Quality indicators in laboratory medicine: state-of-the-art, quality specifications and future strategies, Clinical chemistry and laboratory medicine, 2023
• Palmer J, Galior K: Defining allowable total error limits in the clinical laboratory, Advances in clinical chemistry, 2024
• Miller WG, Jones GR, Horowitz GL et al: Proficiency testing/external quality assessment: current challenges and future directions, Clinical chemistry, 2011