PLR (platelet/lymphocyte)

Platelets are the small cell fragments that make your blood clot, but they do more: with inflammation your liver makes a signal substance that sets the bone marrow to more platelets, and the count rises over days to weeks. An iron deficiency lifts them too. Lymphocytes are the specialists of your immune system, and cortisol pulls them out of the blood back to the lymph nodes with stress, illness and lack of sleep. The PLR divides one by the other, so the ratio rises when there is inflammation that has been running a while and the immune system is under pressure at the same time. That makes the PLR the slow counterpart of the NLR. Neutrophils live a day and respond within hours; platelets live a week or ten days and respond over days to weeks. A high NLR with a normal PLR is therefore a fresh load, a bad night or an infection just starting; a high PLR with a high NLR is a load that has lasted longer. Together with CRP, which measures the inflammation itself, the two ratios tell how long something has been going on. Your report usually does not print the ratio; you calculate it yourself with the calculator on this page. The only study that publishes a reference interval comes out at 49 to 198 for adults and gives older adults from age 70 a lower interval of 42 to 187, because platelets fall somewhat with age.

The PLR is a measure of load that has lasted a while. Anyone who sleeps badly for months, structurally trains too much or has an inflammation that does not stop, in the gut, the joints or the gums, sees the platelets slowly rise and the lymphocytes fall, and the ratio rises. A smouldering inflammation from belly fat, smoking and little exercise does the same in milder form. A PLR that stays at the high end over the years therefore goes with more cardiovascular disease, and it falls along with lifestyle. The second reason is that the ratio brings together two numbers you would otherwise read separately. Platelets that sit at the high end through an iron deficiency, and lymphocytes that sit at the low end through a heavy period, each still fall within their band, but the ratio between the two shows that two things are going on at once. That is why the PLR says more in the same person over several measurements than in one measurement against an interval. The honest limitation is the same as with the NLR: the ratio does not say which of the two numbers moved. A high PLR can come from platelets that have risen through an iron deficiency, from lymphocytes suppressed by prednisone, or from an inflammation that did both. That is why you always read it beside the separate numbers, beside ferritin and beside CRP.

A low PLR means the lymphocytes dominate or the platelets are low. More lymphocytes is usually a virus or the recovery phase after it, and then the ratio is temporarily low. Fewer platelets is a virus that has just passed, plenty of alcohol, a medicine, or rarely a bone marrow that makes less; then look at the platelets themselves, because they say more than the ratio. Below 49 the question is which of the two it was. A high PLR means something is going on that has lasted a while, and the question is what. Above 198 with a high CRP it is an inflammation or an infection that has been running for days to weeks, and then the ratio falls with recovery. With a low ferritin it is an iron deficiency that lifts the platelets. Without inflammation and without iron deficiency it is load: a period of poor sleep, overtraining, chronic stress, smoking or prednisone. A ratio that stays at the high end over several measurements without explanation you read beside the platelets themselves, because those are looked at too if they stay high without reason. Always read the PLR beside the platelets and lymphocytes themselves, because the ratio does not say which of the two moved, beside the NLR, which measures the same balance faster, beside CRP, which says whether inflammation is running, and beside ferritin, which says whether an iron deficiency is lifting the platelets.